diff --git a/composer.json b/composer.json
index 2fad9e0b5..71300a921 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,8 @@
         "ext-mongodb": ">=0.6.0"
     },
     "autoload": {
-        "psr-4": { "MongoDB\\": "src/" }
+        "psr-4": { "MongoDB\\": "src/" },
+        "files": [ "src/functions.php" ]
     },
     "extra": {
         "branch-alias": {
diff --git a/src/Client.php b/src/Client.php
index 8386addf3..4031ed11e 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -7,9 +7,9 @@
 use MongoDB\Driver\Manager;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Model\DatabaseInfoIterator;
-use MongoDB\Model\DatabaseInfoLegacyIterator;
+use MongoDB\Operation\DropDatabase;
+use MongoDB\Operation\ListDatabases;
 
 class Client
 {
@@ -37,45 +37,29 @@ public function __construct($uri, array $options = array(), array $driverOptions
     /**
      * Drop a database.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/dropDatabase/
      * @param string $databaseName
-     * @return Cursor
+     * @return object Command result document
      */
     public function dropDatabase($databaseName)
     {
-        $databaseName = (string) $databaseName;
-        $command = new Command(array('dropDatabase' => 1));
-        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
+        $operation = new DropDatabase($databaseName);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        return $this->manager->executeCommand($databaseName, $command, $readPreference);
+        return $operation->execute($server);
     }
 
     /**
      * List databases.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/listDatabases/
+     * @see ListDatabases::__construct() for supported options
      * @return DatabaseInfoIterator
-     * @throws UnexpectedValueException if the command result is malformed
      */
-    public function listDatabases()
+    public function listDatabases(array $options = array())
     {
-        $command = new Command(array('listDatabases' => 1));
+        $operation = new ListDatabases($options);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        $cursor = $this->manager->executeCommand('admin', $command);
-        $cursor->setTypeMap(array('document' => 'array'));
-        $result = current($cursor->toArray());
-
-        if ( ! isset($result['databases']) || ! is_array($result['databases'])) {
-            throw new UnexpectedValueException('listDatabases command did not return a "databases" array');
-        }
-
-        /* Return an Iterator instead of an array in case listDatabases is
-         * eventually changed to return a command cursor, like the collection
-         * and index enumeration commands. This makes the "totalSize" command
-         * field inaccessible, but users can manually invoke the command if they
-         * need that value.
-         */
-        return new DatabaseInfoLegacyIterator($result['databases']);
+        return $operation->execute($server);
     }
 
     /**
diff --git a/src/Collection.php b/src/Collection.php
index b55d1c5b1..8d0d21871 100644
--- a/src/Collection.php
+++ b/src/Collection.php
@@ -13,8 +13,18 @@
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedTypeException;
 use MongoDB\Model\IndexInfoIterator;
-use MongoDB\Model\IndexInfoIteratorIterator;
 use MongoDB\Model\IndexInput;
+use MongoDB\Operation\Aggregate;
+use MongoDB\Operation\CreateIndexes;
+use MongoDB\Operation\Count;
+use MongoDB\Operation\Distinct;
+use MongoDB\Operation\DropCollection;
+use MongoDB\Operation\DropIndexes;
+use MongoDB\Operation\FindOneAndDelete;
+use MongoDB\Operation\FindOneAndReplace;
+use MongoDB\Operation\FindOneAndUpdate;
+use MongoDB\Operation\ListIndexes;
+use Traversable;
 
 class Collection
 {
@@ -33,9 +43,6 @@ class Collection
     //self::QUERY_FLAG_TAILABLE_CURSOR | self::QUERY_FLAG_AWAIT_DATA;
     const CURSOR_TYPE_TAILABLE_AWAIT = 0x22;
 
-    const FIND_ONE_AND_RETURN_BEFORE = 0x01;
-    const FIND_ONE_AND_RETURN_AFTER  = 0x02;
-
     protected $manager;
     protected $ns;
     protected $wc;
@@ -78,79 +85,25 @@ public function __toString()
     }
 
     /**
-     * Runs an aggregation framework pipeline
+     * Executes an aggregation framework pipeline on the collection.
      *
      * Note: this method's return value depends on the MongoDB server version
      * and the "useCursor" option. If "useCursor" is true, a Cursor will be
      * returned; otherwise, an ArrayIterator is returned, which wraps the
      * "result" array from the command response document.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/aggregate/
-     *
-     * @param array $pipeline The pipeline to execute
-     * @param array $options  Additional options
-     * @return Iterator
+     * @see Aggregate::__construct() for supported options
+     * @param array $pipeline List of pipeline operations
+     * @param array $options  Command options
+     * @return Traversable
      */
     public function aggregate(array $pipeline, array $options = array())
     {
         $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
         $server = $this->manager->selectServer($readPreference);
+        $operation = new Aggregate($this->dbname, $this->collname, $pipeline, $options);
 
-        if (FeatureDetection::isSupported($server, FeatureDetection::API_AGGREGATE_CURSOR)) {
-            $options = array_merge(
-                array(
-                    /**
-                     * Enables writing to temporary files. When set to true, aggregation stages
-                     * can write data to the _tmp subdirectory in the dbPath directory. The
-                     * default is false.
-                     *
-                     * @see http://docs.mongodb.org/manual/reference/command/aggregate/
-                     */
-                    'allowDiskUse' => false,
-                    /**
-                     * The number of documents to return per batch.
-                     *
-                     * @see http://docs.mongodb.org/manual/reference/command/aggregate/
-                     */
-                    'batchSize' => 0,
-                    /**
-                     * The maximum amount of time to allow the query to run.
-                     *
-                     * @see http://docs.mongodb.org/manual/reference/command/aggregate/
-                     */
-                    'maxTimeMS' => 0,
-                    /**
-                     * Indicates if the results should be provided as a cursor.
-                     *
-                     * @see http://docs.mongodb.org/manual/reference/command/aggregate/
-                     */
-                    'useCursor' => true,
-                ),
-                $options
-            );
-        }
-
-        $options = $this->_massageAggregateOptions($options);
-        $command = new Command(array(
-            'aggregate' => $this->collname,
-            'pipeline' => $pipeline,
-        ) + $options);
-        $cursor = $server->executeCommand($this->dbname, $command);
-
-        if ( ! empty($options["cursor"])) {
-            return $cursor;
-        }
-
-        $doc = current($cursor->toArray());
-
-        if ($doc["ok"]) {
-            return new \ArrayIterator(array_map(
-                function (\stdClass $document) { return (array) $document; },
-                $doc["result"]
-            ));
-        }
-
-        throw $this->_generateCommandException($doc);
+        return $operation->execute($server);
     }
 
     /**
@@ -286,35 +239,24 @@ public function bulkWrite(array $ops, array $options = array())
     }
 
     /**
-     * Counts all documents matching $filter
-     * If no $filter provided, returns the numbers of documents in the collection
+     * Gets the number of documents matching the filter.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/count/
-     * @see Collection::getCountOptions() for supported $options
-     *
-     * @param array $filter   The find query to execute
-     * @param array $options  Additional options
+     * @see Count::__construct() for supported options
+     * @param array $filter  Query by which to filter documents
+     * @param array $options Command options
      * @return integer
      */
     public function count(array $filter = array(), array $options = array())
     {
-        $cmd = array(
-            "count" => $this->collname,
-            "query" => (object) $filter,
-        ) + $options;
-
-        $doc = current($this->_runCommand($this->dbname, $cmd)->toArray());
-        if ($doc["ok"]) {
-            return (integer) $doc["n"];
-        }
-        throw $this->_generateCommandException($doc);
+        $operation = new Count($this->dbname, $this->collname, $filter, $options);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+
+        return $operation->execute($server);
     }
 
     /**
      * Create a single index for the collection.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/createIndexes/
-     * @see http://docs.mongodb.org/manual/reference/method/db.collection.createIndex/
      * @see Collection::createIndexes()
      * @param array|object $key     Document containing fields mapped to values,
      *                              which denote order or an index type
@@ -345,34 +287,16 @@ public function createIndex($key, array $options = array())
      *
      * @see http://docs.mongodb.org/manual/reference/command/createIndexes/
      * @see http://docs.mongodb.org/manual/reference/method/db.collection.createIndex/
-     * @param array $indexes List of index specifications
+     * @param array[] $indexes List of index specifications
      * @return string[] The names of the created indexes
      * @throws InvalidArgumentException if an index specification is invalid
      */
     public function createIndexes(array $indexes)
     {
-        if (empty($indexes)) {
-            return array();
-        }
-
-        foreach ($indexes as $i => $index) {
-            if ( ! is_array($index)) {
-                throw new UnexpectedTypeException($index, 'array');
-            }
-
-            if ( ! isset($index['ns'])) {
-                $index['ns'] = $this->ns;
-            }
-
-            $indexes[$i] = new IndexInput($index);
-        }
-
-        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
-        $server = $this->manager->selectServer($readPreference);
+        $operation = new CreateIndexes($this->dbname, $this->collname, $indexes);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        return (FeatureDetection::isSupported($server, FeatureDetection::API_CREATEINDEXES_CMD))
-            ? $this->createIndexesCommand($server, $indexes)
-            : $this->createIndexesLegacy($server, $indexes);
+        return $operation->execute($server);
     }
 
     /**
@@ -408,86 +332,67 @@ public function deleteOne(array $filter)
     }
 
     /**
-     * Finds the distinct values for a specified field across the collection
+     * Finds the distinct values for a specified field across the collection.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/distinct/
-     * @see Collection::getDistinctOptions() for supported $options
-     *
-     * @param string $fieldName  The fieldname to use
-     * @param array $filter      The find query to execute
-     * @param array $options     Additional options
-     * @return integer
+     * @see Distinct::__construct() for supported options
+     * @param string $fieldName Field for which to return distinct values
+     * @param array  $filter    Query by which to filter documents
+     * @param array  $options   Command options
+     * @return mixed[]
      */
     public function distinct($fieldName, array $filter = array(), array $options = array())
     {
-        $options = array_merge($this->getDistinctOptions(), $options);
-        $cmd = array(
-            "distinct" => $this->collname,
-            "key"      => $fieldName,
-            "query"    => (object) $filter,
-        ) + $options;
-
-        $doc = current($this->_runCommand($this->dbname, $cmd)->toArray());
-        if ($doc["ok"]) {
-            return $doc["values"];
-        }
-        throw $this->_generateCommandException($doc);
+        $operation = new Distinct($this->dbname, $this->collname, $fieldName, $filter, $options);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+
+        return $operation->execute($server);
     }
 
     /**
      * Drop this collection.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/drop/
-     * @return Cursor
+     * @return object Command result document
      */
     public function drop()
     {
-        $command = new Command(array('drop' => $this->collname));
-        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
+        $operation = new DropCollection($this->dbname, $this->collname);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        return $this->manager->executeCommand($this->dbname, $command, $readPreference);
+        return $operation->execute($server);
     }
 
     /**
      * Drop a single index in the collection.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/dropIndexes/
-     * @see http://docs.mongodb.org/manual/reference/method/db.collection.dropIndex/
-     * @param string $indexName
-     * @return Cursor
+     * @param string $indexName Index name
+     * @return object Command result document
      * @throws InvalidArgumentException if $indexName is an empty string or "*"
      */
     public function dropIndex($indexName)
     {
         $indexName = (string) $indexName;
 
-        if ($indexName === '') {
-            throw new InvalidArgumentException('Index name cannot be empty');
-        }
-
         if ($indexName === '*') {
             throw new InvalidArgumentException('dropIndexes() must be used to drop multiple indexes');
         }
 
-        $command = new Command(array('dropIndexes' => $this->collname, 'index' => $indexName));
-        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
+        $operation = new DropIndexes($this->dbname, $this->collname, $indexName);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        return $this->manager->executeCommand($this->dbname, $command, $readPreference);
+        return $operation->execute($server);
     }
 
     /**
      * Drop all indexes in the collection.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/dropIndexes/
-     * @see http://docs.mongodb.org/manual/reference/method/db.collection.dropIndexes/
-     * @return Cursor
+     * @return object Command result document
      */
     public function dropIndexes()
     {
-        $command = new Command(array('dropIndexes' => $this->collname, 'index' => '*'));
-        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
+        $operation = new DropIndexes($this->dbname, $this->collname, '*');
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        return $this->manager->executeCommand($this->dbname, $command, $readPreference);
+        return $operation->execute($server);
     }
 
     /**
@@ -540,103 +445,63 @@ public function findOne(array $filter = array(), array $options = array())
     /**
      * Finds a single document and deletes it, returning the original.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-     * @see Collection::getFindOneAndDelete() for supported $options
+     * The document to return may be null.
      *
-     * @param array $filter   The $filter criteria to search for
-     * @param array $options  Additional options
-     * @return array The original document
+     * @see FindOneAndDelete::__construct() for supported options
+     * @param array|object $filter  Query by which to filter documents
+     * @param array        $options Command options
+     * @return object|null
      */
-    public function findOneAndDelete(array $filter, array $options = array())
+    public function findOneAndDelete($filter, array $options = array())
     {
-        $options = array_merge($this->getFindOneAndDeleteOptions(), $options);
-        $options = $this->_massageFindAndModifyOptions($options);
-        $cmd = array(
-            "findandmodify" => $this->collname,
-            "query"         => $filter,
-        ) + $options;
-
-        $doc = current($this->_runCommand($this->dbname, $cmd)->toArray());
-        if ($doc["ok"]) {
-            return is_object($doc["value"]) ? (array) $doc["value"] : $doc["value"];
-        }
+        $operation = new FindOneAndDelete($this->dbname, $this->collname, $filter, $options);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        throw $this->_generateCommandException($doc);
+        return $operation->execute($server);
     }
 
     /**
-     * Finds a single document and replaces it, returning either the original or the replaced document
-     * By default, returns the original document.
-     * To return the new document set:
-     *     $options = array("returnDocument" => Collection::FIND_ONE_AND_RETURN_AFTER);
+     * Finds a single document and replaces it, returning either the original or
+     * the replaced document.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-     * @see Collection::getFindOneAndReplace() for supported $options
+     * The document to return may be null. By default, the original document is
+     * returned. Specify FindOneAndReplace::RETURN_DOCUMENT_AFTER for the
+     * "returnDocument" option to return the updated document.
      *
-     * @param array $filter       The $filter criteria to search for
-     * @param array $replacement  The document to replace with
-     * @param array $options      Additional options
-     * @return array
+     * @see FindOneAndReplace::__construct() for supported options
+     * @param array|object $filter      Query by which to filter documents
+     * @param array|object $replacement Replacement document
+     * @param array        $options     Command options
+     * @return object|null
      */
-    public function findOneAndReplace(array $filter, array $replacement, array $options = array())
+    public function findOneAndReplace($filter, $replacement, array $options = array())
     {
-        $firstKey = key($replacement);
-        if (isset($firstKey[0]) && $firstKey[0] == '$') {
-            throw new InvalidArgumentException("First key in \$replacement must NOT be a \$operator");
-        }
-
-        $options = array_merge($this->getFindOneAndReplaceOptions(), $options);
-        $options = $this->_massageFindAndModifyOptions($options, $replacement);
-
-        $cmd = array(
-            "findandmodify" => $this->collname,
-            "query"         => $filter,
-        ) + $options;
+        $operation = new FindOneAndReplace($this->dbname, $this->collname, $filter, $replacement, $options);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        $doc = current($this->_runCommand($this->dbname, $cmd)->toArray());
-        if ($doc["ok"]) {
-            return $this->_massageFindAndModifyResult($doc, $options);
-        }
-
-        throw $this->_generateCommandException($doc);
+        return $operation->execute($server);
     }
 
     /**
-     * Finds a single document and updates it, returning either the original or the updated document
-     * By default, returns the original document.
-     * To return the new document set:
-     *     $options = array("returnDocument" => Collection::FIND_ONE_AND_RETURN_AFTER);
+     * Finds a single document and updates it, returning either the original or
+     * the updated document.
      *
+     * The document to return may be null. By default, the original document is
+     * returned. Specify FindOneAndUpdate::RETURN_DOCUMENT_AFTER for the
+     * "returnDocument" option to return the updated document.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-     * @see Collection::getFindOneAndUpdate() for supported $options
-     *
-     * @param array $filter   The $filter criteria to search for
-     * @param array $update   An array of update operators to apply to the document
-     * @param array $options  Additional options
-     * @return array
+     * @see FindOneAndReplace::__construct() for supported options
+     * @param array|object $filter  Query by which to filter documents
+     * @param array|object $update  Update to apply to the matched document
+     * @param array        $options Command options
+     * @return object|null
      */
-    public function findOneAndUpdate(array $filter, array $update, array $options = array())
+    public function findOneAndUpdate($filter, $update, array $options = array())
     {
-        $firstKey = key($update);
-        if (!isset($firstKey[0]) || $firstKey[0] != '$') {
-            throw new InvalidArgumentException("First key in \$update must be a \$operator");
-        }
-
-        $options = array_merge($this->getFindOneAndUpdateOptions(), $options);
-        $options = $this->_massageFindAndModifyOptions($options, $update);
-
-        $cmd = array(
-            "findandmodify" => $this->collname,
-            "query"         => $filter,
-        ) + $options;
-
-        $doc = current($this->_runCommand($this->dbname, $cmd)->toArray());
-        if ($doc["ok"]) {
-            return $this->_massageFindAndModifyResult($doc, $options);
-        }
+        $operation = new FindOneAndUpdate($this->dbname, $this->collname, $filter, $update, $options);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        throw $this->_generateCommandException($doc);
+        return $operation->execute($server);
     }
 
     /**
@@ -661,44 +526,6 @@ public function getCollectionName()
         return $this->collname;
     }
 
-    /**
-     * Retrieves all count options with their default values.
-     *
-     * @return array of Collection::count() options
-     */
-    public function getCountOptions()
-    {
-        return array(
-            /**
-             * The index to use.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/count/
-             */
-            "hint" => "", // string or document
-
-            /**
-             * The maximum number of documents to count.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/count/
-             */
-            "limit" => 0,
-
-            /**
-             * The maximum amount of time to allow the query to run.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/count/
-             */
-            "maxTimeMS" => 0,
-
-            /**
-             * The number of documents to skip before returning the documents.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/count/
-             */
-            "skip"  => 0,
-        );
-    }
-
     /**
      * Return the database name.
      *
@@ -709,150 +536,6 @@ public function getDatabaseName()
         return $this->dbname;
     }
 
-    /**
-     * Retrieves all distinct options with their default values.
-     *
-     * @return array of Collection::distinct() options
-     */
-    public function getDistinctOptions()
-    {
-        return array(
-            /**
-             * The maximum amount of time to allow the query to run. The default is infinite.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/distinct/
-             */
-            "maxTimeMS" => 0,
-        );
-    }
-
-    /**
-     * Retrieves all findOneDelete options with their default values.
-     *
-     * @return array of Collection::findOneAndDelete() options
-     */
-    public function getFindOneAndDeleteOptions()
-    {
-        return array(
-
-            /**
-             * The maximum amount of time to allow the query to run.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-             */
-            "maxTimeMS" => 0,
-
-            /**
-             * Limits the fields to return for all matching documents.
-             *
-             * @see http://docs.mongodb.org/manual/tutorial/project-fields-from-query-results
-             */
-            "projection" => array(),
-
-            /**
-             * Determines which document the operation modifies if the query selects multiple documents.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-             */
-            "sort" => array(),
-        );
-    }
-
-    /**
-     * Retrieves all findOneAndReplace options with their default values.
-     *
-     * @return array of Collection::findOneAndReplace() options
-     */
-    public function getFindOneAndReplaceOptions()
-    {
-        return array(
-
-            /**
-             * The maximum amount of time to allow the query to run.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-             */
-            "maxTimeMS" => 0,
-
-            /**
-             * Limits the fields to return for all matching documents.
-             *
-             * @see http://docs.mongodb.org/manual/tutorial/project-fields-from-query-results
-             */
-            "projection" => array(),
-
-            /**
-             * When ReturnDocument.After, returns the replaced or inserted document rather than the original.
-             * Defaults to ReturnDocument.Before.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-             */
-            "returnDocument" => self::FIND_ONE_AND_RETURN_BEFORE,
-
-            /**
-             * Determines which document the operation modifies if the query selects multiple documents.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-             */
-            "sort" => array(),
-
-            /**
-             * When true, findAndModify creates a new document if no document matches the query. The
-             * default is false.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-             */
-            "upsert" => false,
-        );
-    }
-
-    /**
-     * Retrieves all findOneAndUpdate options with their default values.
-     *
-     * @return array of Collection::findOneAndUpdate() options
-     */
-    public function getFindOneAndUpdateOptions()
-    {
-        return array(
-
-            /**
-             * The maximum amount of time to allow the query to run.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-             */
-            "maxTimeMS" => 0,
-
-            /**
-             * Limits the fields to return for all matching documents.
-             *
-             * @see http://docs.mongodb.org/manual/tutorial/project-fields-from-query-results
-             */
-            "projection" => array(),
-
-            /**
-             * When ReturnDocument.After, returns the updated or inserted document rather than the original.
-             * Defaults to ReturnDocument.Before.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-             */
-            "returnDocument" => self::FIND_ONE_AND_RETURN_BEFORE,
-
-            /**
-             * Determines which document the operation modifies if the query selects multiple documents.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-             */
-            "sort" => array(),
-
-            /**
-             * When true, creates a new document if no document matches the query. The default is false.
-             *
-             * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
-             */
-            "upsert" => false,
-        );
-    }
-
     /**
      * Retrieves all find options with their default values.
      *
@@ -1035,18 +718,15 @@ public function insertOne($document)
     /**
      * Returns information for all indexes for the collection.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/listIndexes/
-     * @see http://docs.mongodb.org/manual/reference/method/db.collection.getIndexes/
+     * @see ListIndexes::__construct() for supported options
      * @return IndexInfoIterator
      */
-    public function listIndexes()
+    public function listIndexes(array $options = array())
     {
-        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
-        $server = $this->manager->selectServer($readPreference);
+        $operation = new ListIndexes($this->dbname, $this->collname, $options);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        return (FeatureDetection::isSupported($server, FeatureDetection::API_LISTINDEXES_CMD))
-            ? $this->listIndexesCommand($server)
-            : $this->listIndexesLegacy($server);
+        return $operation->execute($server);
     }
 
     /**
@@ -1155,85 +835,6 @@ final protected function _delete($filter, $limit = 1)
         return $this->manager->executeBulkWrite($this->ns, $bulk, $this->wc);
     }
 
-    /**
-     * Internal helper for throwing an exception with error message
-     * @internal
-     */
-    final protected function _generateCommandException($doc)
-    {
-        if ($doc["errmsg"]) {
-            return new RuntimeException($doc["errmsg"]);
-        }
-        var_dump($doc);
-        return new RuntimeException("FIXME: Unknown error");
-    }
-
-    /**
-     * Internal helper for massaging aggregate options
-     * @internal
-     */
-    protected function _massageAggregateOptions($options)
-    {
-        if ( ! empty($options["useCursor"])) {
-            $options["cursor"] = isset($options["batchSize"])
-                ? array("batchSize" => (integer) $options["batchSize"])
-                : new stdClass;
-        }
-        unset($options["useCursor"], $options["batchSize"]);
-
-        return $options;
-    }
-
-    /**
-     * Internal helper for massaging findandmodify options
-     * @internal
-     */
-    final protected function _massageFindAndModifyOptions($options, $update = array())
-    {
-        $ret = array(
-            "sort"   => $options["sort"],
-            "new"    => isset($options["returnDocument"]) ? $options["returnDocument"] == self::FIND_ONE_AND_RETURN_AFTER : false,
-            "fields" => $options["projection"],
-            "upsert" => isset($options["upsert"]) ? $options["upsert"] : false,
-        );
-        if ($update) {
-            $ret["update"] = $update;
-        } else {
-            $ret["remove"] = true;
-        }
-        return $ret;
-    }
-
-    /**
-     * Internal helper for massaging the findAndModify result.
-     *
-     * @internal
-     * @param array $result
-     * @param array $options
-     * @return array|null
-     */
-    final protected function _massageFindAndModifyResult(array $result, array $options)
-    {
-        if ($result['value'] === null) {
-            return null;
-        }
-
-        /* Prior to 3.0, findAndModify returns an empty document instead of null
-         * when an upsert is performed and the pre-modified document was
-         * requested.
-         */
-        if ($options['upsert'] && ! $options['new'] &&
-            isset($result['lastErrorObject']->updatedExisting) &&
-            ! $result['lastErrorObject']->updatedExisting) {
-
-            return null;
-        }
-
-        return is_object($result["value"])
-            ? (array) $result['value']
-            : $result['value'];
-    }
-
     /**
      * Constructs the Query Wire Protocol field 'flags' based on $options
      * provided to other helpers
@@ -1254,17 +855,6 @@ final protected function _opQueryFlags($options)
         return $flags;
     }
 
-    /**
-     * Internal helper for running a command
-     * @internal
-     */
-    final protected function _runCommand($dbname, array $cmd, ReadPreference $rp = null)
-    {
-        //var_dump(\BSON\toJSON(\BSON\fromArray($cmd)));
-        $command = new Command($cmd);
-        return $this->manager->executeCommand($dbname, $command, $rp);
-    }
-
     /**
      * Internal helper for replacing/updating one/many documents
      * @internal
@@ -1277,77 +867,4 @@ protected function _update($filter, $update, $options)
         $bulk->update($filter, $update, $options);
         return $this->manager->executeBulkWrite($this->ns, $bulk, $this->wc);
     }
-
-    /**
-     * Create one or more indexes for the collection using the createIndexes
-     * command.
-     *
-     * @param Server       $server
-     * @param IndexInput[] $indexes
-     * @return string[] The names of the created indexes
-     */
-    private function createIndexesCommand(Server $server, array $indexes)
-    {
-        $command = new Command(array(
-            'createIndexes' => $this->collname,
-            'indexes' => $indexes,
-        ));
-        $server->executeCommand($this->dbname, $command);
-
-        return array_map(function(IndexInput $index) { return (string) $index; }, $indexes);
-    }
-
-    /**
-     * Create one or more indexes for the collection by inserting into the
-     * "system.indexes" collection (MongoDB <2.6).
-     *
-     * @param Server       $server
-     * @param IndexInput[] $indexes
-     * @return string[] The names of the created indexes
-     */
-    private function createIndexesLegacy(Server $server, array $indexes)
-    {
-        $bulk = new BulkWrite(true);
-
-        foreach ($indexes as $index) {
-            $bulk->insert($index);
-        }
-
-        $server->executeBulkWrite($this->dbname . '.system.indexes', $bulk);
-
-        return array_map(function(IndexInput $index) { return (string) $index; }, $indexes);
-    }
-
-    /**
-     * Returns information for all indexes for this collection using the
-     * listIndexes command.
-     *
-     * @see http://docs.mongodb.org/manual/reference/command/listIndexes/
-     * @param Server $server
-     * @return IndexInfoIteratorIterator
-     */
-    private function listIndexesCommand(Server $server)
-    {
-        $command = new Command(array('listIndexes' => $this->collname));
-        $cursor = $server->executeCommand($this->dbname, $command);
-        $cursor->setTypeMap(array('document' => 'array'));
-
-        return new IndexInfoIteratorIterator($cursor);
-    }
-
-    /**
-     * Returns information for all indexes for this collection by querying the
-     * "system.indexes" collection (MongoDB <2.8).
-     *
-     * @param Server $server
-     * @return IndexInfoIteratorIterator
-     */
-    private function listIndexesLegacy(Server $server)
-    {
-        $query = new Query(array('ns' => $this->ns));
-        $cursor = $server->executeQuery($this->dbname . '.system.indexes', $query);
-        $cursor->setTypeMap(array('document' => 'array'));
-
-        return new IndexInfoIteratorIterator($cursor);
-    }
 }
diff --git a/src/Database.php b/src/Database.php
index 8ca8d11c4..7724d9777 100644
--- a/src/Database.php
+++ b/src/Database.php
@@ -12,8 +12,10 @@
 use MongoDB\Driver\WriteConcern;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Model\CollectionInfoIterator;
-use MongoDB\Model\CollectionInfoCommandIterator;
-use MongoDB\Model\CollectionInfoLegacyIterator;
+use MongoDB\Operation\CreateCollection;
+use MongoDB\Operation\DropCollection;
+use MongoDB\Operation\DropDatabase;
+use MongoDB\Operation\ListCollections;
 
 class Database
 {
@@ -54,49 +56,44 @@ public function __toString()
     /**
      * Create a new collection explicitly.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/create/
-     * @see http://docs.mongodb.org/manual/reference/method/db.createCollection/
+     * @see CreateCollection::__construct() for supported options
      * @param string $collectionName
      * @param array  $options
-     * @return Cursor
+     * @return object Command result document
      */
     public function createCollection($collectionName, array $options = array())
     {
-        $collectionName = (string) $collectionName;
-        $command = new Command(array('create' => $collectionName) + $options);
-        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
+        $operation = new CreateCollection($this->databaseName, $collectionName, $options);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        return $this->manager->executeCommand($this->databaseName, $command, $readPreference);
+        return $operation->execute($server);
     }
 
     /**
      * Drop this database.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/dropDatabase/
-     * @return Cursor
+     * @return object Command result document
      */
     public function drop()
     {
-        $command = new Command(array('dropDatabase' => 1));
-        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
+        $operation = new DropDatabase($this->databaseName);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        return $this->manager->executeCommand($this->databaseName, $command, $readPreference);
+        return $operation->execute($server);
     }
 
     /**
      * Drop a collection within this database.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/drop/
      * @param string $collectionName
-     * @return Cursor
+     * @return object Command result document
      */
     public function dropCollection($collectionName)
     {
-        $collectionName = (string) $collectionName;
-        $command = new Command(array('drop' => $collectionName));
-        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
+        $operation = new DropCollection($this->databaseName, $collectionName);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        return $this->manager->executeCommand($this->databaseName, $command, $readPreference);
+        return $operation->execute($server);
     }
 
     /**
@@ -112,18 +109,16 @@ public function getDatabaseName()
     /**
      * Returns information for all collections in this database.
      *
-     * @see http://docs.mongodb.org/manual/reference/command/listCollections/
+     * @see ListCollections::__construct() for supported options
      * @param array $options
      * @return CollectionInfoIterator
      */
     public function listCollections(array $options = array())
     {
-        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
-        $server = $this->manager->selectServer($readPreference);
+        $operation = new ListCollections($this->databaseName, $options);
+        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        return (FeatureDetection::isSupported($server, FeatureDetection::API_LISTCOLLECTIONS_CMD))
-            ? $this->listCollectionsCommand($server, $options)
-            : $this->listCollectionsLegacy($server, $options);
+        return $operation->execute($server);
     }
 
     /**
@@ -145,58 +140,4 @@ public function selectCollection($collectionName, WriteConcern $writeConcern = n
 
         return new Collection($this->manager, $namespace, $writeConcern, $readPreference);
     }
-
-    /**
-     * Returns information for all collections in this database using the
-     * listCollections command.
-     *
-     * @param Server $server
-     * @param array  $options
-     * @return CollectionInfoCommandIterator
-     */
-    private function listCollectionsCommand(Server $server, array $options = array())
-    {
-        $command = new Command(array('listCollections' => 1) + $options);
-        $cursor = $server->executeCommand($this->databaseName, $command);
-        $cursor->setTypeMap(array('document' => 'array'));
-
-        return new CollectionInfoCommandIterator($cursor);
-    }
-
-    /**
-     * Returns information for all collections in this database by querying the
-     * "system.namespaces" collection (MongoDB <2.8).
-     *
-     * @param Server $server
-     * @param array  $options
-     * @return CollectionInfoLegacyIterator
-     * @throws InvalidArgumentException if the filter option is neither an array
-     *                                  nor object, or if filter.name is not a
-     *                                  string.
-     */
-    private function listCollectionsLegacy(Server $server, array $options = array())
-    {
-        $filter = array_key_exists('filter', $options) ? $options['filter'] : array();
-
-        if ( ! is_array($filter) && ! is_object($filter)) {
-            throw new InvalidArgumentException(sprintf('Expected filter to be array or object, %s given', gettype($filter)));
-        }
-
-        if (array_key_exists('name', (array) $filter)) {
-            $filter = (array) $filter;
-
-            if ( ! is_string($filter['name'])) {
-                throw new InvalidArgumentException(sprintf('Filter "name" must be a string for MongoDB <2.8, %s given', gettype($filter['name'])));
-            }
-
-            $filter['name'] = $this->databaseName . '.' . $filter['name'];
-        }
-
-        $namespace = $this->databaseName . '.system.namespaces';
-        $query = new Query($filter);
-        $cursor = $server->executeQuery($namespace, $query);
-        $cursor->setTypeMap(array('document' => 'array'));
-
-        return new CollectionInfoLegacyIterator($cursor);
-    }
 }
diff --git a/src/Exception/InvalidArgumentTypeException.php b/src/Exception/InvalidArgumentTypeException.php
new file mode 100644
index 000000000..9bc580c10
--- /dev/null
+++ b/src/Exception/InvalidArgumentTypeException.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace MongoDB\Exception;
+
+class InvalidArgumentTypeException extends InvalidArgumentException
+{
+    public function __construct($name, $value, $expectedType)
+    {
+        parent::__construct(sprintf('Expected %s to have type "%s" but found "%s"', $name, $expectedType, is_object($value) ? get_class($value) : gettype($value)));
+    }
+}
diff --git a/src/Exception/UnexpectedValueTypeException.php b/src/Exception/UnexpectedValueTypeException.php
new file mode 100644
index 000000000..a754b25e1
--- /dev/null
+++ b/src/Exception/UnexpectedValueTypeException.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace MongoDB\Exception;
+
+class UnexpectedValueTypeException extends UnexpectedValueException
+{
+    public function __construct($name, $value, $expectedType)
+    {
+        parent::__construct(sprintf('Expected %s to have type "%s" but found "%s"', $name, $expectedType, is_object($value) ? get_class($value) : gettype($value)));
+    }
+}
diff --git a/src/FeatureDetection.php b/src/FeatureDetection.php
deleted file mode 100644
index 418bef75d..000000000
--- a/src/FeatureDetection.php
+++ /dev/null
@@ -1,34 +0,0 @@
-<?php
-
-namespace MongoDB;
-
-use MongoDB\Driver\Server;
-
-/**
- * Utility class for detecting features based on wire protocol versions.
- *
- * @internal
- */
-class FeatureDetection
-{
-    const API_LISTCOLLECTIONS_CMD = 3;
-    const API_LISTINDEXES_CMD = 3;
-    const API_CREATEINDEXES_CMD = 2;
-    const API_AGGREGATE_CURSOR = 2;
-
-    /**
-     * Return whether the server supports a particular feature.
-     *
-     * @param Server  $server  Server to check
-     * @param integer $feature Feature constant (i.e. wire protocol version)
-     * @return boolean
-     */
-    static public function isSupported(Server $server, $feature)
-    {
-        $info = $server->getInfo();
-        $maxWireVersion = isset($info['maxWireVersion']) ? (integer) $info['maxWireVersion'] : 0;
-        $minWireVersion = isset($info['minWireVersion']) ? (integer) $info['minWireVersion'] : 0;
-
-        return ($minWireVersion <= $feature && $maxWireVersion >= $feature);
-    }
-}
diff --git a/src/Model/IndexInput.php b/src/Model/IndexInput.php
index dc6338f7e..db4288992 100644
--- a/src/Model/IndexInput.php
+++ b/src/Model/IndexInput.php
@@ -50,7 +50,7 @@ public function __construct(array $index)
         }
 
         if ( ! isset($index['name'])) {
-            $index['name'] = $this->generateName($index['key']);
+            $index['name'] = \MongoDB\generate_index_name($index['key']);
         }
 
         if ( ! is_string($index['name'])) {
@@ -80,22 +80,4 @@ public function bsonSerialize()
     {
         return $this->index;
     }
-
-    /**
-     * Generates an index name from its key specification.
-     *
-     * @param array|object $key Document containing fields mapped to values,
-     *                          which denote order or an index type
-     * @return string
-     */
-    private function generateName($key)
-    {
-        $name = '';
-
-        foreach ($key as $field => $type) {
-            $name .= ($name != '' ? '_' : '') . $field . '_' . $type;
-        }
-
-        return $name;
-    }
 }
diff --git a/src/Operation/Aggregate.php b/src/Operation/Aggregate.php
new file mode 100644
index 000000000..37621d34c
--- /dev/null
+++ b/src/Operation/Aggregate.php
@@ -0,0 +1,174 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\InvalidArgumentTypeException;
+use MongoDB\Exception\RuntimeException;
+use MongoDB\Exception\UnexpectedValueException;
+use ArrayIterator;
+use stdClass;
+use Traversable;
+
+/**
+ * Operation for the aggregate command.
+ *
+ * @api
+ * @see MongoDB\Collection::aggregate()
+ * @see http://docs.mongodb.org/manual/reference/command/aggregate/
+ */
+class Aggregate implements Executable
+{
+    private static $wireVersionForCursor = 2;
+
+    private $databaseName;
+    private $collectionName;
+    private $pipeline;
+    private $options;
+
+    /**
+     * Constructs an aggregate command.
+     *
+     * Supported options:
+     *
+     *  * allowDiskUse (boolean): Enables writing to temporary files. When set
+     *    to true, aggregation stages can write data to the _tmp sub-directory
+     *    in the dbPath directory. The default is false.
+     *
+     *  * batchSize (integer): The number of documents to return per batch.
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     *  * useCursor (boolean): Indicates whether the command will request that
+     *    the server provide results using a cursor. The default is true.
+     *
+     *    For servers < 2.6, this option is ignored as aggregation cursors are
+     *    not available.
+     *
+     *    For servers >= 2.6, this option allows users to turn off cursors if
+     *    necessary to aid in mongod/mongos upgrades.
+     *
+     * @param string $databaseName   Database name
+     * @param string $collectionName Collection name
+     * @param array  $pipeline       List of pipeline operations
+     * @param array  $options        Command options
+     * @throws InvalidArgumentException
+     */
+    public function __construct($databaseName, $collectionName, array $pipeline, array $options = array())
+    {
+        $options += array(
+            'allowDiskUse' => false,
+            'useCursor' => true,
+        );
+
+        if ( ! is_bool($options['allowDiskUse'])) {
+            throw new InvalidArgumentTypeException('"allowDiskUse" option', $options['allowDiskUse'], 'boolean');
+        }
+
+        if (isset($options['batchSize']) && ! is_integer($options['batchSize'])) {
+            throw new InvalidArgumentTypeException('"batchSize" option', $options['batchSize'], 'integer');
+        }
+
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        if ( ! is_bool($options['useCursor'])) {
+            throw new InvalidArgumentTypeException('"useCursor" option', $options['useCursor'], 'boolean');
+        }
+
+        if (isset($options['batchSize']) && ! $options['useCursor']) {
+            throw new InvalidArgumentException('"batchSize" option should not be used if "useCursor" is false');
+        }
+
+        $expectedIndex = 0;
+
+        foreach ($pipeline as $i => $op) {
+            if ($i !== $expectedIndex) {
+                throw new InvalidArgumentException(sprintf('$pipeline is not a list (unexpected index: "%s")', $i));
+            }
+
+            if ( ! is_array($op) && ! is_object($op)) {
+                throw new InvalidArgumentTypeException(sprintf('$pipeline[%d]', $i), $op, 'array or object');
+            }
+
+            $expectedIndex += 1;
+        }
+
+        $this->databaseName = (string) $databaseName;
+        $this->collectionName = (string) $collectionName;
+        $this->pipeline = $pipeline;
+        $this->options = $options;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return Traversable
+     */
+    public function execute(Server $server)
+    {
+        $isCursorSupported = \MongoDB\server_supports_feature($server, self::$wireVersionForCursor);
+
+        $command = $this->createCommand($server, $isCursorSupported);
+        $cursor = $server->executeCommand($this->databaseName, $command);
+
+        if ($isCursorSupported && $this->options['useCursor']) {
+            return $cursor;
+        }
+
+        $result = current($cursor->toArray());
+
+        if (empty($result['ok'])) {
+            throw new RuntimeException(isset($result['errmsg']) ? $result['errmsg'] : 'Unknown error');
+        }
+
+        if ( ! isset($result['result']) || ! is_array($result['result'])) {
+            throw new UnexpectedValueException('aggregate command did not return a "result" array');
+        }
+
+        return new ArrayIterator(array_map(
+            function (stdClass $document) { return (array) $document; },
+            $result['result']
+        ));
+    }
+
+    /**
+     * Create the aggregate command.
+     *
+     * @param Server  $server
+     * @param boolean $isCursorSupported
+     * @return Command
+     */
+    private function createCommand(Server $server, $isCursorSupported)
+    {
+        $cmd = array(
+            'aggregate' => $this->collectionName,
+            'pipeline' => $this->pipeline,
+        );
+
+        // Servers < 2.6 do not support any command options
+        if ( ! $isCursorSupported) {
+            return new Command($cmd);
+        }
+
+        $cmd['allowDiskUse'] = $this->options['allowDiskUse'];
+
+        if (isset($this->options['maxTimeMS'])) {
+            $cmd['maxTimeMS'] = $this->options['maxTimeMS'];
+        }
+
+        if ($this->options['useCursor']) {
+            $cmd['cursor'] = isset($this->options["batchSize"])
+                ? array('batchSize' => $this->options["batchSize"])
+                : new stdClass;
+        }
+
+        return new Command($cmd);
+    }
+}
diff --git a/src/Operation/Count.php b/src/Operation/Count.php
new file mode 100644
index 000000000..137fd47d9
--- /dev/null
+++ b/src/Operation/Count.php
@@ -0,0 +1,125 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\InvalidArgumentTypeException;
+use MongoDB\Exception\RuntimeException;
+use MongoDB\Exception\UnexpectedValueException;
+
+/**
+ * Operation for the count command.
+ *
+ * @api
+ * @see MongoDB\Collection::count()
+ * @see http://docs.mongodb.org/manual/reference/command/count/
+ */
+class Count implements Executable
+{
+    private $databaseName;
+    private $collectionName;
+    private $filter;
+    private $options;
+
+    /**
+     * Constructs a count command.
+     *
+     * Supported options:
+     *
+     *  * hint (string|document): The index to use. If a document, it will be
+     *    interpretted as an index specification and a name will be generated.
+     *
+     *  * limit (integer): The maximum number of documents to count.
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     *  * skip (integer): The number of documents to skip before returning the
+     *    documents.
+     *
+     * @param string $databaseName   Database name
+     * @param string $collectionName Collection name
+     * @param array  $filter         Query by which to filter documents
+     * @param array  $options        Command options
+     * @throws InvalidArgumentException
+     */
+    public function __construct($databaseName, $collectionName, array $filter = array(), array $options = array())
+    {
+        if (isset($options['hint'])) {
+            if (is_array($options['hint']) || is_object($options['hint'])) {
+                $options['hint'] = \MongoDB\generate_index_name($options['hint']);
+            }
+
+            if ( ! is_string($options['hint'])) {
+                throw new InvalidArgumentTypeException('"hint" option', $options['hint'], 'string or array or object');
+            }
+        }
+
+        if (isset($options['limit']) && ! is_integer($options['limit'])) {
+            throw new InvalidArgumentTypeException('"limit" option', $options['limit'], 'integer');
+        }
+
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        if (isset($options['skip']) && ! is_integer($options['skip'])) {
+            throw new InvalidArgumentTypeException('"skip" option', $options['skip'], 'integer');
+        }
+
+        $this->databaseName = (string) $databaseName;
+        $this->collectionName = (string) $collectionName;
+        $this->filter = $filter;
+        $this->options = $options;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return integer
+     */
+    public function execute(Server $server)
+    {
+        $cursor = $server->executeCommand($this->databaseName, $this->createCommand());
+        $result = current($cursor->toArray());
+
+        if (empty($result['ok'])) {
+            throw new RuntimeException(isset($result['errmsg']) ? $result['errmsg'] : 'Unknown error');
+        }
+
+        // Older server versions may return a float
+        if ( ! isset($result['n']) || ! (is_integer($result['n']) || is_float($result['n']))) {
+            throw new UnexpectedValueException('count command did not return an "n" value');
+        }
+
+        return (integer) $result['n'];
+    }
+
+    /**
+     * Create the count command.
+     *
+     * @return Command
+     */
+    private function createCommand()
+    {
+        $cmd = array(
+            'count' => $this->collectionName,
+        );
+
+        if ( ! empty($this->filter)) {
+            $cmd['query'] = (object) $this->filter;
+        }
+
+        foreach (array('hint', 'limit', 'maxTimeMS', 'skip') as $option) {
+            if (isset($this->options[$option])) {
+                $cmd[$option] = $this->options[$option];
+            }
+        }
+
+        return new Command($cmd);
+    }
+}
diff --git a/src/Operation/CreateCollection.php b/src/Operation/CreateCollection.php
new file mode 100644
index 000000000..8b71d388c
--- /dev/null
+++ b/src/Operation/CreateCollection.php
@@ -0,0 +1,139 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Driver\BulkWrite;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\RuntimeException;
+use MongoDB\Exception\UnexpectedTypeException;
+use MongoDB\Model\IndexInput;
+
+/**
+ * Operation for the create command.
+ *
+ * @api
+ * @see MongoDB\Database::createCollection()
+ * @see http://docs.mongodb.org/manual/reference/command/create/
+ */
+class CreateCollection implements Executable
+{
+    const USE_POWER_OF_2_SIZES = 1;
+    const NO_PADDING = 2;
+
+    private $databaseName;
+    private $collectionName;
+    private $options = array();
+
+    /**
+     * Constructs a create command.
+     *
+     * Supported options:
+     *
+     *  * autoIndexId (boolean): Specify false to disable the automatic creation
+     *    of an index on the _id field. For replica sets, this option cannot be
+     *    false. The default is true.
+     *
+     *  * capped (boolean): Specify true to create a capped collection. If set,
+     *    the size option must also be specified. The default is false.
+     *
+     *  * flags (integer): Options for the MMAPv1 storage engine only. Must be a
+     *    bitwise combination USE_POWER_OF_2_SIZES and NO_PADDING. The default
+     *    is USE_POWER_OF_2_SIZES.
+     *
+     *  * max (integer): The maximum number of documents allowed in the capped
+     *    collection. The size option takes precedence over this limit.
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     *  * size (integer): The maximum number of bytes for a capped collection.
+     *
+     *  * storageEngine (document): Storage engine options.
+     *
+     * @see http://source.wiredtiger.com/2.4.1/struct_w_t___s_e_s_s_i_o_n.html#a358ca4141d59c345f401c58501276bbb
+     * @param string $databaseName   Database name
+     * @param string $collectionName Collection name
+     * @param array  $options        Command options
+     * @throws InvalidArgumentException
+     */
+    public function __construct($databaseName, $collectionName, array $options = array())
+    {
+        if (isset($options['autoIndexId']) && ! is_bool($options['autoIndexId'])) {
+            throw new InvalidArgumentTypeException('"autoIndexId" option', $options['autoIndexId'], 'boolean');
+        }
+
+        if (isset($options['capped']) && ! is_bool($options['capped'])) {
+            throw new InvalidArgumentTypeException('"capped" option', $options['capped'], 'boolean');
+        }
+
+        if (isset($options['flags']) && ! is_integer($options['flags'])) {
+            throw new InvalidArgumentTypeException('"flags" option', $options['flags'], 'integer');
+        }
+
+        if (isset($options['max']) && ! is_integer($options['max'])) {
+            throw new InvalidArgumentTypeException('"max" option', $options['max'], 'integer');
+        }
+
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        if (isset($options['size']) && ! is_integer($options['size'])) {
+            throw new InvalidArgumentTypeException('"size" option', $options['size'], 'integer');
+        }
+
+        if (isset($options['storageEngine']) && ! is_array($options['storageEngine']) && ! is_object($options['storageEngine'])) {
+            throw new InvalidArgumentTypeException('"storageEngine" option', $options['storageEngine'], 'array or object');
+        }
+
+        $this->databaseName = (string) $databaseName;
+        $this->collectionName = (string) $collectionName;
+        $this->options = $options;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * For servers < 2.6, this will actually perform an insert operation on the
+     * database's "system.indexes" collection.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return object Command result document
+     */
+    public function execute(Server $server)
+    {
+        $cursor = $server->executeCommand($this->databaseName, $this->createCommand());
+        $result = current($cursor->toArray());
+
+        if (empty($result['ok'])) {
+            throw new RuntimeException(isset($result['errmsg']) ? $result['errmsg'] : 'Unknown error');
+        }
+
+        return $result;
+    }
+
+    /**
+     * Create the create command.
+     *
+     * @return Command
+     */
+    private function createCommand()
+    {
+        $cmd = array('create' => $this->collectionName);
+
+        foreach (array('autoIndexId', 'capped', 'flags', 'max', 'maxTimeMS', 'size') as $option) {
+            if (isset($this->options[$option])) {
+                $cmd[$option] = $this->options[$option];
+            }
+        }
+
+        if ( ! empty($this->options['storageEngine'])) {
+            $cmd['storageEngine'] = (object) $this->options['storageEngine'];
+        }
+
+        return new Command($cmd);
+    }
+}
diff --git a/src/Operation/CreateIndexes.php b/src/Operation/CreateIndexes.php
new file mode 100644
index 000000000..858d31e8b
--- /dev/null
+++ b/src/Operation/CreateIndexes.php
@@ -0,0 +1,118 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Driver\BulkWrite;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\RuntimeException;
+use MongoDB\Exception\UnexpectedTypeException;
+use MongoDB\Model\IndexInput;
+
+/**
+ * Operation for the createIndexes command.
+ *
+ * @api
+ * @see MongoDB\Collection::createIndex()
+ * @see MongoDB\Collection::createIndexes()
+ * @see http://docs.mongodb.org/manual/reference/command/createIndexes/
+ */
+class CreateIndexes implements Executable
+{
+    private static $wireVersionForCommand = 2;
+
+    private $databaseName;
+    private $collectionName;
+    private $indexes = array();
+
+    /**
+     * Constructs a createIndexes command.
+     *
+     * @param string  $databaseName   Database name
+     * @param string  $collectionName Collection name
+     * @param array[] $indexes        List of index specifications
+     * @throws InvalidArgumentException
+     */
+    public function __construct($databaseName, $collectionName, array $indexes)
+    {
+        if (empty($indexes)) {
+            throw new InvalidArgumentException('$indexes is empty');
+        }
+
+        foreach ($indexes as $index) {
+            if ( ! is_array($index)) {
+                throw new UnexpectedTypeException($index, 'array');
+            }
+
+            if ( ! isset($index['ns'])) {
+                $index['ns'] = $databaseName . '.' . $collectionName;
+            }
+
+            $this->indexes[] = new IndexInput($index);
+        }
+
+        $this->databaseName = (string) $databaseName;
+        $this->collectionName = (string) $collectionName;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * For servers < 2.6, this will actually perform an insert operation on the
+     * database's "system.indexes" collection.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return string[] The names of the created indexes
+     */
+    public function execute(Server $server)
+    {
+        if (\MongoDB\server_supports_feature($server, self::$wireVersionForCommand)) {
+            $this->executeCommand($server);
+        } else {
+            $this->executeLegacy($server);
+        }
+
+        return array_map(function(IndexInput $index) { return (string) $index; }, $this->indexes);
+    }
+
+    /**
+     * Create one or more indexes for the collection using the createIndexes
+     * command.
+     *
+     * @param Server $server
+     */
+    private function executeCommand(Server $server)
+    {
+        $command = new Command(array(
+            'createIndexes' => $this->collectionName,
+            'indexes' => $this->indexes,
+        ));
+
+        $cursor = $server->executeCommand($this->databaseName, $command);
+        $result = current($cursor->toArray());
+
+        if (empty($result['ok'])) {
+            throw new RuntimeException(isset($result['errmsg']) ? $result['errmsg'] : 'Unknown error');
+        }
+    }
+
+    /**
+     * Create one or more indexes for the collection by inserting into the
+     * "system.indexes" collection (MongoDB <2.6).
+     *
+     * @param Server $server
+     * @param IndexInput[] $indexes
+     */
+    private function executeLegacy(Server $server)
+    {
+        $bulk = new BulkWrite(true);
+
+        foreach ($this->indexes as $index) {
+            $bulk->insert($index);
+        }
+
+        $server->executeBulkWrite($this->databaseName . '.system.indexes', $bulk);
+    }
+}
diff --git a/src/Operation/Distinct.php b/src/Operation/Distinct.php
new file mode 100644
index 000000000..576627054
--- /dev/null
+++ b/src/Operation/Distinct.php
@@ -0,0 +1,100 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\InvalidArgumentTypeException;
+use MongoDB\Exception\RuntimeException;
+use MongoDB\Exception\UnexpectedValueException;
+
+/**
+ * Operation for the distinct command.
+ *
+ * @api
+ * @see MongoDB\Collection::distinct()
+ * @see http://docs.mongodb.org/manual/reference/command/distinct/
+ */
+class Distinct implements Executable
+{
+    private $databaseName;
+    private $collectionName;
+    private $fieldName;
+    private $filter;
+    private $options;
+
+    /**
+     * Constructs a distinct command.
+     *
+     * Supported options:
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     * @param string $databaseName   Database name
+     * @param string $collectionName Collection name
+     * @param string $fieldName      Field for which to return distinct values
+     * @param array  $filter         Query by which to filter documents
+     * @param array  $options        Command options
+     * @throws InvalidArgumentException
+     */
+    public function __construct($databaseName, $collectionName, $fieldName, array $filter = array(), array $options = array())
+    {
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        $this->databaseName = (string) $databaseName;
+        $this->collectionName = (string) $collectionName;
+        $this->fieldName = (string) $fieldName;
+        $this->filter = $filter;
+        $this->options = $options;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return mixed[]
+     */
+    public function execute(Server $server)
+    {
+        $cursor = $server->executeCommand($this->databaseName, $this->createCommand());
+        $result = current($cursor->toArray());
+
+        if (empty($result['ok'])) {
+            throw new RuntimeException(isset($result['errmsg']) ? $result['errmsg'] : 'Unknown error');
+        }
+
+        if ( ! isset($result['values']) || ! is_array($result['values'])) {
+            throw new UnexpectedValueException('distinct command did not return a "values" array');
+        }
+
+        return $result['values'];
+    }
+
+    /**
+     * Create the distinct command.
+     *
+     * @return Command
+     */
+    private function createCommand()
+    {
+        $cmd = array(
+            'distinct' => $this->collectionName,
+            'key' => $this->fieldName,
+        );
+
+        if ( ! empty($this->filter)) {
+            $cmd['query'] = (object) $this->filter;
+        }
+
+        if (isset($this->options['maxTimeMS'])) {
+            $cmd[$option] = $this->options['maxTimeMS'];
+        }
+
+        return new Command($cmd);
+    }
+}
diff --git a/src/Operation/DropCollection.php b/src/Operation/DropCollection.php
new file mode 100644
index 000000000..437ccfcb1
--- /dev/null
+++ b/src/Operation/DropCollection.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\RuntimeException;
+
+/**
+ * Operation for the drop command.
+ *
+ * @api
+ * @see MongoDB\Collection::drop()
+ * @see MongoDB\Database::dropCollection()
+ * @see http://docs.mongodb.org/manual/reference/command/drop/
+ */
+class DropCollection implements Executable
+{
+    private $databaseName;
+    private $collectionName;
+
+    /**
+     * Constructs a drop command.
+     *
+     * @param string $databaseName   Database name
+     * @param string $collectionName Collection name
+     */
+    public function __construct($databaseName, $collectionName)
+    {
+        $this->databaseName = (string) $databaseName;
+        $this->collectionName = (string) $collectionName;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return object Command result document
+     */
+    public function execute(Server $server)
+    {
+        $cursor = $server->executeCommand($this->databaseName, new Command(array('drop' => $this->collectionName)));
+        $result = current($cursor->toArray());
+
+        if (empty($result['ok'])) {
+            throw new RuntimeException(isset($result['errmsg']) ? $result['errmsg'] : 'Unknown error');
+        }
+
+        return $result;
+    }
+}
diff --git a/src/Operation/DropDatabase.php b/src/Operation/DropDatabase.php
new file mode 100644
index 000000000..4c4313d3e
--- /dev/null
+++ b/src/Operation/DropDatabase.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\RuntimeException;
+
+/**
+ * Operation for the dropDatabase command.
+ *
+ * @api
+ * @see MongoDB\Client::dropDatabase()
+ * @see MongoDB\Database::drop()
+ * @see http://docs.mongodb.org/manual/reference/command/dropDatabase/
+ */
+class DropDatabase implements Executable
+{
+    private $databaseName;
+
+    /**
+     * Constructs a dropDatabase command.
+     *
+     * @param string $databaseName   Database name
+     * @param string $collectionName Collection name
+     */
+    public function __construct($databaseName)
+    {
+        $this->databaseName = (string) $databaseName;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return object Command result document
+     */
+    public function execute(Server $server)
+    {
+        $cursor = $server->executeCommand($this->databaseName, new Command(array('dropDatabase' => 1)));
+        $result = current($cursor->toArray());
+
+        if (empty($result['ok'])) {
+            throw new RuntimeException(isset($result['errmsg']) ? $result['errmsg'] : 'Unknown error');
+        }
+
+        return $result;
+    }
+}
diff --git a/src/Operation/DropIndexes.php b/src/Operation/DropIndexes.php
new file mode 100644
index 000000000..78ab4de6e
--- /dev/null
+++ b/src/Operation/DropIndexes.php
@@ -0,0 +1,67 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\RuntimeException;
+
+/**
+ * Operation for the dropIndexes command.
+ *
+ * @api
+ * @see MongoDB\Collection::dropIndexes()
+ * @see http://docs.mongodb.org/manual/reference/command/dropIndexes/
+ */
+class DropIndexes implements Executable
+{
+    private $databaseName;
+    private $collectionName;
+    private $indexName;
+
+    /**
+     * Constructs a dropIndexes command.
+     *
+     * @param string $databaseName   Database name
+     * @param string $collectionName Collection name
+     * @param string $indexName      Index name (use "*" to drop all indexes)
+     * @throws InvalidArgumentException
+     */
+    public function __construct($databaseName, $collectionName, $indexName)
+    {
+        $indexName = (string) $indexName;
+
+        if ($indexName === '') {
+            throw new InvalidArgumentException('$indexName cannot be empty');
+        }
+
+        $this->databaseName = (string) $databaseName;
+        $this->collectionName = (string) $collectionName;
+        $this->indexName = $indexName;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return object Command result document
+     */
+    public function execute(Server $server)
+    {
+        $cmd = array(
+            'dropIndexes' => $this->collectionName,
+            'index' => $this->indexName,
+        );
+
+        $cursor = $server->executeCommand($this->databaseName, new Command($cmd));
+        $result = current($cursor->toArray());
+
+        if (empty($result['ok'])) {
+            throw new RuntimeException(isset($result['errmsg']) ? $result['errmsg'] : 'Unknown error');
+        }
+
+        return $result;
+    }
+}
diff --git a/src/Operation/Executable.php b/src/Operation/Executable.php
new file mode 100644
index 000000000..4ef501d4e
--- /dev/null
+++ b/src/Operation/Executable.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Server;
+
+/**
+ * Executable interface for operation classes.
+ *
+ * @api
+ */
+interface Executable
+{
+    /**
+     * Execute the operation.
+     *
+     * @param Server $server
+     * @return mixed
+     */
+    public function execute(Server $server);
+}
diff --git a/src/Operation/FindAndModify.php b/src/Operation/FindAndModify.php
new file mode 100644
index 000000000..0c288b058
--- /dev/null
+++ b/src/Operation/FindAndModify.php
@@ -0,0 +1,179 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\InvalidArgumentTypeException;
+use MongoDB\Exception\RuntimeException;
+use MongoDB\Exception\UnexpectedValueException;
+
+/**
+ * Operation for the findAndModify command.
+ *
+ * This class is used internally by the FindOneAndDelete, FindOneAndReplace, and
+ * FindOneAndUpdate operation classes.
+ *
+ * @internal
+ * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
+ */
+class FindAndModify implements Executable
+{
+    private $databaseName;
+    private $collectionName;
+    private $options;
+
+    /**
+     * Constructs a findAndModify command.
+     *
+     * Supported options:
+     *
+     *  * fields (document): Limits the fields to return for the matching
+     *    document.
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     *  * new (boolean): When true, returns the modified document rather than
+     *    the original. This option is ignored for remove operations. The
+     *    The default is false.
+     *
+     *  * query (document): Query by which to filter documents.
+     *
+     *  * remove (boolean): When true, removes the matched document. This option
+     *    cannot be true if the update option is set. The default is false.
+     *
+     *  * sort (document): Determines which document the operation modifies if
+     *    the query selects multiple documents.
+     *
+     *  * update (document): Update or replacement to apply to the matched
+     *    document. This option cannot be set if the remove option is true.
+     *
+     *  * upsert (boolean): When true, a new document is created if no document
+     *    matches the query. This option is ignored for remove operations. The
+     *    default is false.
+     *
+     * @param string $databaseName   Database name
+     * @param string $collectionName Collection name
+     * @param array  $options        Command options
+     * @throws InvalidArgumentException
+     */
+    public function __construct($databaseName, $collectionName, array $options)
+    {
+        $options += array(
+            'new' => false,
+            'remove' => false,
+            'upsert' => false,
+        );
+
+        if (isset($options['fields']) && ! is_array($options['fields']) && ! is_object($options['fields'])) {
+            throw new InvalidArgumentTypeException('"fields" option', $options['fields'], 'array or object');
+        }
+
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        if ( ! is_bool($options['new'])) {
+            throw new InvalidArgumentTypeException('"new" option', $options['new'], 'boolean');
+        }
+
+        if (isset($options['query']) && ! is_array($options['query']) && ! is_object($options['query'])) {
+            throw new InvalidArgumentTypeException('"query" option', $options['query'], 'array or object');
+        }
+
+        if ( ! is_bool($options['remove'])) {
+            throw new InvalidArgumentTypeException('"remove" option', $options['remove'], 'boolean');
+        }
+
+        if (isset($options['sort']) && ! is_array($options['sort']) && ! is_object($options['sort'])) {
+            throw new InvalidArgumentTypeException('"sort" option', $options['sort'], 'array or object');
+        }
+
+        if (isset($options['update']) && ! is_array($options['update']) && ! is_object($options['update'])) {
+            throw new InvalidArgumentTypeException('"update" option', $options['update'], 'array or object');
+        }
+
+        if ( ! is_bool($options['upsert'])) {
+            throw new InvalidArgumentTypeException('"upsert" option', $options['upsert'], 'boolean');
+        }
+
+        if ( ! (isset($options['update']) xor $options['remove'])) {
+            throw new InvalidArgumentException('The "remove" option must be true or an "update" document must be specified, but not both');
+        }
+
+        $this->databaseName = (string) $databaseName;
+        $this->collectionName = (string) $collectionName;
+        $this->options = $options;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return object|null
+     */
+    public function execute(Server $server)
+    {
+        $cursor = $server->executeCommand($this->databaseName, $this->createCommand());
+        $result = current($cursor->toArray());
+
+        if (empty($result['ok'])) {
+            throw new RuntimeException(isset($result['errmsg']) ? $result['errmsg'] : 'Unknown error');
+        }
+
+        if ( ! isset($result['value'])) {
+            return null;
+        }
+
+        /* Prior to 3.0, findAndModify returns an empty document instead of null
+         * when an upsert is performed and the pre-modified document was
+         * requested.
+         */
+        if ($this->options['upsert'] && ! $this->options['new'] &&
+            isset($result['lastErrorObject']->updatedExisting) &&
+            ! $result['lastErrorObject']->updatedExisting) {
+
+            return null;
+        }
+
+        if ( ! is_object($result['value'])) {
+            throw new UnexpectedValueException('findAndModify command did not return a "value" document');
+        }
+
+        return $result['value'];
+    }
+
+    /**
+     * Create the findAndModify command.
+     *
+     * @return Command
+     */
+    private function createCommand()
+    {
+        $cmd = array(
+            'findAndModify' => $this->collectionName,
+        );
+
+        if ($this->options['remove']) {
+            $cmd['remove'] = true;
+        } else {
+            $cmd['new'] = $this->options['new'];
+            $cmd['upsert'] = $this->options['upsert'];
+        }
+
+        foreach (array('fields', 'query', 'sort', 'update') as $option) {
+            if (isset($this->options[$option])) {
+                $cmd[$option] = (object) $this->options[$option];
+            }
+        }
+
+        if (isset($this->options['maxTimeMS'])) {
+            $cmd['maxTimeMS'] = $this->options['maxTimeMS'];
+        }
+
+        return new Command($cmd);
+    }
+}
diff --git a/src/Operation/FindOneAndDelete.php b/src/Operation/FindOneAndDelete.php
new file mode 100644
index 000000000..4ff1cf88a
--- /dev/null
+++ b/src/Operation/FindOneAndDelete.php
@@ -0,0 +1,83 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\InvalidArgumentTypeException;
+
+/**
+ * Operation for deleting a document with the findAndModify command.
+ *
+ * @api
+ * @see MongoDB\Collection::findOneAndDelete()
+ * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
+ */
+class FindOneAndDelete implements Executable
+{
+    private $findAndModify;
+
+    /**
+     * Constructs a findAndModify command for deleting a document.
+     *
+     * Supported options:
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     *  * projection (document): Limits the fields to return for the matching
+     *    document.
+     *
+     *  * sort (document): Determines which document the operation modifies if
+     *    the query selects multiple documents.
+     *
+     * @param string       $databaseName   Database name
+     * @param string       $collectionName Collection name
+     * @param array|object $filter         Query by which to filter documents
+     * @param array        $options        Command options
+     * @throws InvalidArgumentException
+     */
+    public function __construct($databaseName, $collectionName, $filter, array $options = array())
+    {
+        if ( ! is_array($filter) && ! is_object($filter)) {
+            throw new InvalidArgumentTypeException('$filter', $filter, 'array or object');
+        }
+
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        if (isset($options['projection']) && ! is_array($options['projection']) && ! is_object($options['projection'])) {
+            throw new InvalidArgumentTypeException('"projection" option', $options['projection'], 'array or object');
+        }
+
+        if (isset($options['sort']) && ! is_array($options['sort']) && ! is_object($options['sort'])) {
+            throw new InvalidArgumentTypeException('"sort" option', $options['sort'], 'array or object');
+        }
+
+        $this->findAndModify = new FindAndModify(
+            $databaseName,
+            $collectionName,
+            array(
+                'fields' => isset($options['projection']) ? $options['projection'] : null,
+                'maxTimeMS' => isset($options['maxTimeMS']) ? $options['maxTimeMS'] : null,
+                'query' => $filter,
+                'remove' => true,
+                'sort' => isset($options['sort']) ? $options['sort'] : null,
+            )
+        );
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return object|null
+     */
+    public function execute(Server $server)
+    {
+        return $this->findAndModify->execute($server);
+    }
+}
diff --git a/src/Operation/FindOneAndReplace.php b/src/Operation/FindOneAndReplace.php
new file mode 100644
index 000000000..dbf834360
--- /dev/null
+++ b/src/Operation/FindOneAndReplace.php
@@ -0,0 +1,122 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\InvalidArgumentTypeException;
+
+/**
+ * Operation for replacing a document with the findAndModify command.
+ *
+ * @api
+ * @see MongoDB\Collection::findOneAndReplace()
+ * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
+ */
+class FindOneAndReplace implements Executable
+{
+    const RETURN_DOCUMENT_BEFORE = 1;
+    const RETURN_DOCUMENT_AFTER = 2;
+
+    private $findAndModify;
+
+    /**
+     * Constructs a findAndModify command for replacing a document.
+     *
+     * Supported options:
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     *  * projection (document): Limits the fields to return for the matching
+     *    document.
+     *
+     *  * returnDocument (enum): Whether to return the document before or after
+     *    the update is applied. Must be either RETURN_DOCUMENT_BEFORE or
+     *    RETURN_DOCUMENT_AFTER. The default is RETURN_DOCUMENT_BEFORE.
+     *
+     *  * sort (document): Determines which document the operation modifies if
+     *    the query selects multiple documents.
+     *
+     *  * upsert (boolean): When true, a new document is created if no document
+     *    matches the query. The default is false.
+     *
+     * @param string       $databaseName   Database name
+     * @param string       $collectionName Collection name
+     * @param array|object $filter         Query by which to filter documents
+     * @param array|object $replacement    Replacement document
+     * @param array        $options        Command options
+     * @throws InvalidArgumentException
+     */
+    public function __construct($databaseName, $collectionName, $filter, $replacement, array $options = array())
+    {
+        if ( ! is_array($filter) && ! is_object($filter)) {
+            throw new InvalidArgumentTypeException('$filter', $filter, 'array or object');
+        }
+
+        if ( ! is_array($replacement) && ! is_object($replacement)) {
+            throw new InvalidArgumentTypeException('$replacement', $replacement, 'array or object');
+        }
+
+        if (\MongoDB\is_first_key_operator($replacement)) {
+            throw new InvalidArgumentException('First key in $replacement argument is an update operator');
+        }
+
+        $options += array(
+            'returnDocument' => self::RETURN_DOCUMENT_BEFORE,
+            'upsert' => false,
+        );
+
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        if (isset($options['projection']) && ! is_array($options['projection']) && ! is_object($options['projection'])) {
+            throw new InvalidArgumentTypeException('"projection" option', $options['projection'], 'array or object');
+        }
+
+        if ( ! is_integer($options['returnDocument'])) {
+            throw new InvalidArgumentTypeException('"returnDocument" option', $options['returnDocument'], 'integer');
+        }
+
+        if ($options['returnDocument'] !== self::RETURN_DOCUMENT_AFTER &&
+            $options['returnDocument'] !== self::RETURN_DOCUMENT_BEFORE) {
+            throw new InvalidArgumentException('Invalid value for "returnDocument" option: ' . $options['returnDocument']);
+        }
+
+        if (isset($options['sort']) && ! is_array($options['sort']) && ! is_object($options['sort'])) {
+            throw new InvalidArgumentTypeException('"sort" option', $options['sort'], 'array or object');
+        }
+
+        if ( ! is_bool($options['upsert'])) {
+            throw new InvalidArgumentTypeException('"upsert" option', $options['upsert'], 'boolean');
+        }
+
+        $this->findAndModify = new FindAndModify(
+            $databaseName,
+            $collectionName,
+            array(
+                'fields' => isset($options['projection']) ? $options['projection'] : null,
+                'maxTimeMS' => isset($options['maxTimeMS']) ? $options['maxTimeMS'] : null,
+                'new' => $options['returnDocument'] === self::RETURN_DOCUMENT_AFTER,
+                'query' => $filter,
+                'sort' => isset($options['sort']) ? $options['sort'] : null,
+                'update' => $replacement,
+                'upsert' => $options['upsert'],
+            )
+        );
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return object|null
+     */
+    public function execute(Server $server)
+    {
+        return $this->findAndModify->execute($server);
+    }
+}
diff --git a/src/Operation/FindOneAndUpdate.php b/src/Operation/FindOneAndUpdate.php
new file mode 100644
index 000000000..7bcc05d7b
--- /dev/null
+++ b/src/Operation/FindOneAndUpdate.php
@@ -0,0 +1,122 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\InvalidArgumentTypeException;
+
+/**
+ * Operation for updating a document with the findAndModify command.
+ *
+ * @api
+ * @see MongoDB\Collection::findOneAndUpdate()
+ * @see http://docs.mongodb.org/manual/reference/command/findAndModify/
+ */
+class FindOneAndUpdate implements Executable
+{
+    const RETURN_DOCUMENT_BEFORE = 1;
+    const RETURN_DOCUMENT_AFTER = 2;
+
+    private $findAndModify;
+
+    /**
+     * Constructs a findAndModify command for updating a document.
+     *
+     * Supported options:
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     *  * projection (document): Limits the fields to return for the matching
+     *    document.
+     *
+     *  * returnDocument (enum): Whether to return the document before or after
+     *    the update is applied. Must be either RETURN_DOCUMENT_BEFORE or
+     *    RETURN_DOCUMENT_AFTER. The default is RETURN_DOCUMENT_BEFORE.
+     *
+     *  * sort (document): Determines which document the operation modifies if
+     *    the query selects multiple documents.
+     *
+     *  * upsert (boolean): When true, a new document is created if no document
+     *    matches the query. The default is false.
+     *
+     * @param string       $databaseName   Database name
+     * @param string       $collectionName Collection name
+     * @param array|object $filter         Query by which to filter documents
+     * @param array|object $update         Update to apply to the matched document
+     * @param array        $options        Command options
+     * @throws InvalidArgumentException
+     */
+    public function __construct($databaseName, $collectionName, $filter, $update, array $options = array())
+    {
+        if ( ! is_array($filter) && ! is_object($filter)) {
+            throw new InvalidArgumentTypeException('$filter', $filter, 'array or object');
+        }
+
+        if ( ! is_array($update) && ! is_object($update)) {
+            throw new InvalidArgumentTypeException('$update', $update, 'array or object');
+        }
+
+        if ( ! \MongoDB\is_first_key_operator($update)) {
+            throw new InvalidArgumentException('First key in $update argument is not an update operator');
+        }
+
+        $options += array(
+            'returnDocument' => self::RETURN_DOCUMENT_BEFORE,
+            'upsert' => false,
+        );
+
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        if (isset($options['projection']) && ! is_array($options['projection']) && ! is_object($options['projection'])) {
+            throw new InvalidArgumentTypeException('"projection" option', $options['projection'], 'array or object');
+        }
+
+        if ( ! is_integer($options['returnDocument'])) {
+            throw new InvalidArgumentTypeException('"returnDocument" option', $options['returnDocument'], 'integer');
+        }
+
+        if ($options['returnDocument'] !== self::RETURN_DOCUMENT_AFTER &&
+            $options['returnDocument'] !== self::RETURN_DOCUMENT_BEFORE) {
+            throw new InvalidArgumentException('Invalid value for "returnDocument" option: ' . $options['returnDocument']);
+        }
+
+        if (isset($options['sort']) && ! is_array($options['sort']) && ! is_object($options['sort'])) {
+            throw new InvalidArgumentTypeException('"sort" option', $options['sort'], 'array or object');
+        }
+
+        if ( ! is_bool($options['upsert'])) {
+            throw new InvalidArgumentTypeException('"upsert" option', $options['upsert'], 'boolean');
+        }
+
+        $this->findAndModify = new FindAndModify(
+            $databaseName,
+            $collectionName,
+            array(
+                'fields' => isset($options['projection']) ? $options['projection'] : null,
+                'maxTimeMS' => isset($options['maxTimeMS']) ? $options['maxTimeMS'] : null,
+                'new' => $options['returnDocument'] === self::RETURN_DOCUMENT_AFTER,
+                'query' => $filter,
+                'sort' => isset($options['sort']) ? $options['sort'] : null,
+                'update' => $update,
+                'upsert' => $options['upsert'],
+            )
+        );
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return object|null
+     */
+    public function execute(Server $server)
+    {
+        return $this->findAndModify->execute($server);
+    }
+}
diff --git a/src/Operation/ListCollections.php b/src/Operation/ListCollections.php
new file mode 100644
index 000000000..40a2b3cb6
--- /dev/null
+++ b/src/Operation/ListCollections.php
@@ -0,0 +1,122 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Query;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\RuntimeException;
+use MongoDB\Model\CollectionInfoCommandIterator;
+use MongoDB\Model\CollectionInfoIterator;
+use MongoDB\Model\CollectionInfoLegacyIterator;
+
+/**
+ * Operation for the listCollections command.
+ *
+ * @api
+ * @see MongoDB\Database::listCollections()
+ * @see http://docs.mongodb.org/manual/reference/command/listCollections/
+ */
+class ListCollections implements Executable
+{
+    private static $wireVersionForCommand = 3;
+
+    private $databaseName;
+    private $options;
+
+    /**
+     * Constructs a listCollections command.
+     *
+     * Supported options:
+     *
+     *  * filter (document): Query by which to filter collections.
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     * @param string $databaseName Database name
+     * @param array  $options      Command options
+     */
+    public function __construct($databaseName, array $options = array())
+    {
+        if (isset($options['filter']) && ! is_array($options['filter']) && ! is_object($options['filter'])) {
+            throw new InvalidArgumentTypeException('"filter" option', $options['filter'], 'array or object');
+        }
+
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        $this->databaseName = (string) $databaseName;
+        $this->options = $options;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return CollectionInfoIterator
+     */
+    public function execute(Server $server)
+    {
+        return \MongoDB\server_supports_feature($server, self::$wireVersionForCommand)
+            ? $this->executeCommand($server)
+            : $this->executeLegacy($server);
+    }
+
+    /**
+     * Returns information for all collections in this database using the
+     * listCollections command.
+     *
+     * @param Server $server
+     * @return CollectionInfoCommandIterator
+     */
+    private function executeCommand(Server $server)
+    {
+        $cmd = array('listCollections' => 1);
+
+        if ( ! empty($this->options['filter'])) {
+            $cmd['filter'] = (object) $this->options['filter'];
+        }
+
+        if (isset($this->options['maxTimeMS'])) {
+            $cmd['maxTimeMS'] = $this->options['maxTimeMS'];
+        }
+
+        $cursor = $server->executeCommand($this->databaseName, new Command($cmd));
+        $cursor->setTypeMap(array('document' => 'array'));
+
+        return new CollectionInfoCommandIterator($cursor);
+    }
+
+    /**
+     * Returns information for all collections in this database by querying the
+     * "system.namespaces" collection (MongoDB <3.0).
+     *
+     * @param Server $server
+     * @return CollectionInfoLegacyIterator
+     * @throws InvalidArgumentException if filter.name is not a string.
+     */
+    private function executeLegacy(Server $server)
+    {
+        $filter = empty($this->options['filter']) ? array() : (array) $this->options['filter'];
+
+        if (array_key_exists('name', $filter)) {
+            if ( ! is_string($filter['name'])) {
+                throw new InvalidArgumentTypeException('filter name for MongoDB <3.0', $filter['name'], 'string');
+            }
+
+            $filter['name'] = $this->databaseName . '.' . $filter['name'];
+        }
+
+        $options = isset($this->options['maxTimeMS'])
+            ? array('modifiers' => array('$maxTimeMS' => $this->options['maxTimeMS']))
+            : array();
+
+        $cursor = $server->executeQuery($this->databaseName . '.system.namespaces', new Query($filter, $options));
+        $cursor->setTypeMap(array('document' => 'array'));
+
+        return new CollectionInfoLegacyIterator($cursor);
+    }
+}
diff --git a/src/Operation/ListDatabases.php b/src/Operation/ListDatabases.php
new file mode 100644
index 000000000..1f9f200ed
--- /dev/null
+++ b/src/Operation/ListDatabases.php
@@ -0,0 +1,77 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Server;
+use MongoDB\Exception\RuntimeException;
+use MongoDB\Exception\UnexpectedValueException;
+use MongoDB\Model\DatabaseInfoIterator;
+use MongoDB\Model\DatabaseInfoLegacyIterator;
+
+/**
+ * Operation for the ListDatabases command.
+ *
+ * @api
+ * @see MongoDB\Client::listDatabases()
+ * @see http://docs.mongodb.org/manual/reference/command/ListDatabases/
+ */
+class ListDatabases implements Executable
+{
+    private $options;
+
+    /**
+     * Constructs a listDatabases command.
+     *
+     * Supported options:
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     * @param array $options Command options
+     */
+    public function __construct(array $options = array())
+    {
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        $this->options = $options;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return DatabaseInfoIterator
+     */
+    public function execute(Server $server)
+    {
+        $cmd = array('listDatabases' => 1);
+
+        if (isset($this->options['maxTimeMS'])) {
+            $cmd['maxTimeMS'] = $this->options['maxTimeMS'];
+        }
+
+        $cursor = $server->executeCommand('admin', new Command($cmd));
+        $cursor->setTypeMap(array('document' => 'array'));
+        $result = current($cursor->toArray());
+
+        if (empty($result['ok'])) {
+            throw new RuntimeException(isset($result['errmsg']) ? $result['errmsg'] : 'Unknown error');
+        }
+
+        if ( ! isset($result['databases']) || ! is_array($result['databases'])) {
+            throw new UnexpectedValueException('listDatabases command did not return a "databases" array');
+        }
+
+        /* Return an Iterator instead of an array in case listDatabases is
+         * eventually changed to return a command cursor, like the collection
+         * and index enumeration commands. This makes the "totalSize" command
+         * field inaccessible, but users can manually invoke the command if they
+         * need that value.
+         */
+        return new DatabaseInfoLegacyIterator($result['databases']);
+    }
+}
diff --git a/src/Operation/ListIndexes.php b/src/Operation/ListIndexes.php
new file mode 100644
index 000000000..1e223a010
--- /dev/null
+++ b/src/Operation/ListIndexes.php
@@ -0,0 +1,104 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use MongoDB\Driver\Command;
+use MongoDB\Driver\Query;
+use MongoDB\Driver\Server;
+use MongoDB\Model\IndexInfoIterator;
+use MongoDB\Model\IndexInfoIteratorIterator;
+
+/**
+ * Operation for the listIndexes command.
+ *
+ * @api
+ * @see MongoDB\Collection::listIndexes()
+ * @see http://docs.mongodb.org/manual/reference/command/listIndexes/
+ */
+class ListIndexes implements Executable
+{
+    private static $wireVersionForCommand = 3;
+
+    private $databaseName;
+    private $collectionName;
+    private $options;
+
+    /**
+     * Constructs a listIndexes command.
+     *
+     * Supported options:
+     *
+     *  * maxTimeMS (integer): The maximum amount of time to allow the query to
+     *    run.
+     *
+     * @param string $databaseName   Database name
+     * @param string $collectionName Collection name
+     * @param array  $options        Command options
+     */
+    public function __construct($databaseName, $collectionName, array $options = array())
+    {
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
+            throw new InvalidArgumentTypeException('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
+        }
+
+        $this->databaseName = (string) $databaseName;
+        $this->collectionName = (string) $collectionName;
+        $this->options = $options;
+    }
+
+    /**
+     * Execute the operation.
+     *
+     * @see Executable::execute()
+     * @param Server $server
+     * @return IndexInfoIterator
+     */
+    public function execute(Server $server)
+    {
+        return \MongoDB\server_supports_feature($server, self::$wireVersionForCommand)
+            ? $this->executeCommand($server)
+            : $this->executeLegacy($server);
+    }
+
+    /**
+     * Returns information for all indexes for this collection using the
+     * listIndexes command.
+     *
+     * @param Server $server
+     * @return IndexInfoIteratorIterator
+     */
+    private function executeCommand(Server $server)
+    {
+        $cmd = array('listIndexes' => $this->collectionName);
+
+        if (isset($this->options['maxTimeMS'])) {
+            $cmd['maxTimeMS'] = $this->options['maxTimeMS'];
+        }
+
+        $cursor = $server->executeCommand($this->databaseName, new Command($cmd));
+        $cursor->setTypeMap(array('document' => 'array'));
+
+        return new IndexInfoIteratorIterator($cursor);
+    }
+
+    /**
+     * Returns information for all indexes for this collection by querying the
+     * "system.indexes" collection (MongoDB <3.0).
+     *
+     * @param Server $server
+     * @return IndexInfoIteratorIterator
+     */
+    private function executeLegacy(Server $server)
+    {
+        $filter = array('ns' => $this->databaseName . '.' . $this->collectionName);
+
+        $options = isset($this->options['maxTimeMS'])
+            ? array('modifiers' => array('$maxTimeMS' => $this->options['maxTimeMS']))
+            : array();
+
+        $cursor = $server->executeQuery($this->databaseName . '.system.indexes', new Query($filter, $options));
+        $cursor->setTypeMap(array('document' => 'array'));
+
+        return new IndexInfoIteratorIterator($cursor);
+    }
+}
diff --git a/src/functions.php b/src/functions.php
new file mode 100644
index 000000000..87c246ce9
--- /dev/null
+++ b/src/functions.php
@@ -0,0 +1,76 @@
+<?php
+
+namespace MongoDB;
+
+use MongoDB\Driver\Server;
+use MongoDB\Exception\InvalidArgumentTypeException;
+
+/**
+ * Return whether the first key in the document starts with a "$" character.
+ *
+ * This is used for differentiating update and replacement documents.
+ *
+ * @internal
+ * @param array|object $document Update or replacement document
+ * @return boolean
+ * @throws InvalidArgumentTypeException
+ */
+function is_first_key_operator($document)
+{
+    if (is_object($document)) {
+        $document = get_object_vars($document);
+    }
+
+    if ( ! is_array($document)) {
+        throw new InvalidArgumentTypeException('$document', $document, 'array or object');
+    }
+
+    $firstKey = (string) key($document);
+
+    return (isset($firstKey[0]) && $firstKey[0] == '$');
+}
+
+/**
+ * Generate an index name from a key specification.
+ *
+ * @internal
+ * @param array|object $document Document containing fields mapped to values,
+ *                               which denote order or an index type
+ * @return string
+ * @throws InvalidArgumentTypeException
+ */
+function generate_index_name($document)
+{
+    if (is_object($document)) {
+        $document = get_object_vars($document);
+    }
+
+    if ( ! is_array($document)) {
+        throw new InvalidArgumentTypeException('$document', $document, 'array or object');
+    }
+
+    $name = '';
+
+    foreach ($document as $field => $type) {
+        $name .= ($name != '' ? '_' : '') . $field . '_' . $type;
+    }
+
+    return $name;
+}
+
+/**
+ * Return whether the server supports a particular feature.
+ *
+ * @internal
+ * @param Server  $server  Server to check
+ * @param integer $feature Feature constant (i.e. wire protocol version)
+ * @return boolean
+ */
+function server_supports_feature(Server $server, $feature)
+{
+    $info = $server->getInfo();
+    $maxWireVersion = isset($info['maxWireVersion']) ? (integer) $info['maxWireVersion'] : 0;
+    $minWireVersion = isset($info['minWireVersion']) ? (integer) $info['minWireVersion'] : 0;
+
+    return ($minWireVersion <= $feature && $maxWireVersion >= $feature);
+}
diff --git a/tests/Collection/CrudSpec/AggregateFunctionalTest.php b/tests/Collection/CrudSpec/AggregateFunctionalTest.php
index bdacc989b..183cda284 100644
--- a/tests/Collection/CrudSpec/AggregateFunctionalTest.php
+++ b/tests/Collection/CrudSpec/AggregateFunctionalTest.php
@@ -3,7 +3,6 @@
 namespace MongoDB\Tests\Collection\CrudSpec;
 
 use MongoDB\Collection;
-use MongoDB\FeatureDetection;
 use MongoDB\Driver\ReadPreference;
 
 /**
@@ -13,6 +12,8 @@
  */
 class AggregateFunctionalTest extends FunctionalTestCase
 {
+    private static $wireVersionForOutOperator = 2;
+
     public function setUp()
     {
         parent::setUp();
@@ -36,14 +37,14 @@ public function testAggregateWithMultipleStages()
         );
 
         // Use iterator_to_array() here since aggregate() may return an ArrayIterator
-        $this->assertSame($expected, iterator_to_array($cursor));
+        $this->assertEquals($expected, iterator_to_array($cursor));
     }
 
     public function testAggregateWithOut()
     {
         $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
 
-        if ( ! FeatureDetection::isSupported($server, FeatureDetection::API_AGGREGATE_CURSOR)) {
+        if ( ! \MongoDB\server_supports_feature($server, self::$wireVersionForOutOperator)) {
             $this->markTestSkipped('$out aggregation pipeline operator is not supported');
         }
 
@@ -63,7 +64,7 @@ public function testAggregateWithOut()
             array('_id' => 3, 'x' => 33),
         );
 
-        $this->assertSame($expected, $outputCollection->find()->toArray());
+        $this->assertEquals($expected, $outputCollection->find()->toArray());
 
         // Manually clean up our output collection
         $this->dropCollectionIfItExists($outputCollection);
diff --git a/tests/Collection/CrudSpec/FindOneAndDeleteFunctionalTest.php b/tests/Collection/CrudSpec/FindOneAndDeleteFunctionalTest.php
index 3d5aa9b0a..ecd321220 100644
--- a/tests/Collection/CrudSpec/FindOneAndDeleteFunctionalTest.php
+++ b/tests/Collection/CrudSpec/FindOneAndDeleteFunctionalTest.php
@@ -25,7 +25,7 @@ public function testFindOneAndDeleteWhenManyDocumentsMatch()
         );
 
         $document = $this->collection->findOneAndDelete($filter, $options);
-        $this->assertSame(array('x' => 22), $document);
+        $this->assertEquals((object) array('x' => 22), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
@@ -44,7 +44,7 @@ public function testFindOneAndDeleteWhenOneDocumentMatches()
         );
 
         $document = $this->collection->findOneAndDelete($filter, $options);
-        $this->assertSame(array('x' => 22), $document);
+        $this->assertEquals((object) array('x' => 22), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
diff --git a/tests/Collection/CrudSpec/FindOneAndReplaceFunctionalTest.php b/tests/Collection/CrudSpec/FindOneAndReplaceFunctionalTest.php
index 26c5cf12c..9f4480d2b 100644
--- a/tests/Collection/CrudSpec/FindOneAndReplaceFunctionalTest.php
+++ b/tests/Collection/CrudSpec/FindOneAndReplaceFunctionalTest.php
@@ -3,6 +3,7 @@
 namespace MongoDB\Tests\Collection\CrudSpec;
 
 use MongoDB\Collection;
+use MongoDB\Operation\FindOneAndReplace;
 
 /**
  * CRUD spec functional tests for findOneAndReplace().
@@ -28,7 +29,7 @@ public function testFindOneAndReplaceWhenManyDocumentsMatchReturningDocumentBefo
         );
 
         $document = $this->collection->findOneAndReplace($filter, $replacement, $options);
-        $this->assertSame(array('x' => 22), $document);
+        $this->assertEquals((object) array('x' => 22), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
@@ -46,11 +47,11 @@ public function testFindOneAndReplaceWhenManyDocumentsMatchReturningDocumentAfte
         $options = array(
             'projection' => array('x' => 1, '_id' => 0),
             'sort' => array('x' => 1),
-            'returnDocument' => Collection::FIND_ONE_AND_RETURN_AFTER,
+            'returnDocument' => FindOneAndReplace::RETURN_DOCUMENT_AFTER,
         );
 
         $document = $this->collection->findOneAndReplace($filter, $replacement, $options);
-        $this->assertSame(array('x' => 32), $document);
+        $this->assertEquals((object) array('x' => 32), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
@@ -71,7 +72,7 @@ public function testFindOneAndReplaceWhenOneDocumentMatchesReturningDocumentBefo
         );
 
         $document = $this->collection->findOneAndReplace($filter, $replacement, $options);
-        $this->assertSame(array('x' => 22), $document);
+        $this->assertEquals((object) array('x' => 22), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
@@ -89,11 +90,11 @@ public function testFindOneAndReplaceWhenOneDocumentMatchesReturningDocumentAfte
         $options = array(
             'projection' => array('x' => 1, '_id' => 0),
             'sort' => array('x' => 1),
-            'returnDocument' => Collection::FIND_ONE_AND_RETURN_AFTER,
+            'returnDocument' => FindOneAndReplace::RETURN_DOCUMENT_AFTER,
         );
 
         $document = $this->collection->findOneAndReplace($filter, $replacement, $options);
-        $this->assertSame(array('x' => 32), $document);
+        $this->assertEquals((object) array('x' => 32), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
@@ -156,7 +157,7 @@ public function testFindOneAndReplaceWhenNoDocumentsMatchReturningDocumentAfterM
         $options = array(
             'projection' => array('x' => 1, '_id' => 0),
             'sort' => array('x' => 1),
-            'returnDocument' => Collection::FIND_ONE_AND_RETURN_AFTER,
+            'returnDocument' => FindOneAndReplace::RETURN_DOCUMENT_AFTER,
         );
 
         $document = $this->collection->findOneAndReplace($filter, $replacement, $options);
@@ -179,12 +180,12 @@ public function testFindOneAndReplaceWithUpsertWhenNoDocumentsMatchReturningDocu
         $options = array(
             'projection' => array('x' => 1, '_id' => 0),
             'sort' => array('x' => 1),
-            'returnDocument' => Collection::FIND_ONE_AND_RETURN_AFTER,
+            'returnDocument' => FindOneAndReplace::RETURN_DOCUMENT_AFTER,
             'upsert' => true,
         );
 
         $document = $this->collection->findOneAndReplace($filter, $replacement, $options);
-        $this->assertSame(array('x' => 44), $document);
+        $this->assertEquals((object) array('x' => 44), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
diff --git a/tests/Collection/CrudSpec/FindOneAndUpdateFunctionalTest.php b/tests/Collection/CrudSpec/FindOneAndUpdateFunctionalTest.php
index 10a017da0..c07b9a98c 100644
--- a/tests/Collection/CrudSpec/FindOneAndUpdateFunctionalTest.php
+++ b/tests/Collection/CrudSpec/FindOneAndUpdateFunctionalTest.php
@@ -3,6 +3,7 @@
 namespace MongoDB\Tests\Collection\CrudSpec;
 
 use MongoDB\Collection;
+use MongoDB\Operation\FindOneAndUpdate;
 
 /**
  * CRUD spec functional tests for findOneAndUpdate().
@@ -28,7 +29,7 @@ public function testFindOneAndUpdateWhenManyDocumentsMatchReturningDocumentBefor
         );
 
         $document = $this->collection->findOneAndUpdate($filter, $update, $options);
-        $this->assertSame(array('x' => 22), $document);
+        $this->assertEquals((object) array('x' => 22), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
@@ -46,11 +47,11 @@ public function testFindOneAndUpdateWhenManyDocumentsMatchReturningDocumentAfter
         $options = array(
             'projection' => array('x' => 1, '_id' => 0),
             'sort' => array('x' => 1),
-            'returnDocument' => Collection::FIND_ONE_AND_RETURN_AFTER,
+            'returnDocument' => FindOneAndUpdate::RETURN_DOCUMENT_AFTER,
         );
 
         $document = $this->collection->findOneAndUpdate($filter, $update, $options);
-        $this->assertSame(array('x' => 23), $document);
+        $this->assertEquals((object) array('x' => 23), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
@@ -71,7 +72,7 @@ public function testFindOneAndUpdateWhenOneDocumentMatchesReturningDocumentBefor
         );
 
         $document = $this->collection->findOneAndUpdate($filter, $update, $options);
-        $this->assertSame(array('x' => 22), $document);
+        $this->assertEquals((object) array('x' => 22), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
@@ -89,11 +90,11 @@ public function testFindOneAndUpdateWhenOneDocumentMatchesReturningDocumentAfter
         $options = array(
             'projection' => array('x' => 1, '_id' => 0),
             'sort' => array('x' => 1),
-            'returnDocument' => Collection::FIND_ONE_AND_RETURN_AFTER,
+            'returnDocument' => FindOneAndUpdate::RETURN_DOCUMENT_AFTER,
         );
 
         $document = $this->collection->findOneAndUpdate($filter, $update, $options);
-        $this->assertSame(array('x' => 23), $document);
+        $this->assertEquals((object) array('x' => 23), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
@@ -155,7 +156,7 @@ public function testFindOneAndUpdateWhenNoDocumentsMatchReturningDocumentAfterMo
         $options = array(
             'projection' => array('x' => 1, '_id' => 0),
             'sort' => array('x' => 1),
-            'returnDocument' => Collection::FIND_ONE_AND_RETURN_AFTER,
+            'returnDocument' => FindOneAndUpdate::RETURN_DOCUMENT_AFTER,
         );
 
         $document = $this->collection->findOneAndUpdate($filter, $update, $options);
@@ -177,12 +178,12 @@ public function testFindOneAndUpdateWithUpsertWhenNoDocumentsMatchReturningDocum
         $options = array(
             'projection' => array('x' => 1, '_id' => 0),
             'sort' => array('x' => 1),
-            'returnDocument' => Collection::FIND_ONE_AND_RETURN_AFTER,
+            'returnDocument' => FindOneAndUpdate::RETURN_DOCUMENT_AFTER,
             'upsert' => true,
         );
 
         $document = $this->collection->findOneAndUpdate($filter, $update, $options);
-        $this->assertSame(array('x' => 1), $document);
+        $this->assertEquals((object) array('x' => 1), $document);
 
         $expected = array(
             array('_id' => 1, 'x' => 11),
diff --git a/tests/Collection/IndexManagementFunctionalTest.php b/tests/Collection/IndexManagementFunctionalTest.php
index d91f62918..a9fba6409 100644
--- a/tests/Collection/IndexManagementFunctionalTest.php
+++ b/tests/Collection/IndexManagementFunctionalTest.php
@@ -85,7 +85,10 @@ public function testCreateIndexes()
         });
     }
 
-    public function testCreateIndexesWithEmptyInputIsNop()
+    /**
+     * @expectedException MongoDB\Exception\InvalidArgumentException
+     */
+    public function testCreateIndexesRequiresAtLeastOneIndex()
     {
         $this->assertSame(array(), $this->collection->createIndexes(array()));
     }
diff --git a/tests/FunctionalTestCase.php b/tests/FunctionalTestCase.php
index cdf522e5c..94c98e2f9 100644
--- a/tests/FunctionalTestCase.php
+++ b/tests/FunctionalTestCase.php
@@ -21,15 +21,19 @@ protected function assertCollectionCount($namespace, $count)
         list($databaseName, $collectionName) = explode('.', $namespace, 2);
 
         $cursor = $this->manager->executeCommand($databaseName, new Command(array('count' => $collectionName)));
-
+        $cursor->setTypeMap(array('document' => 'array'));
         $document = current($cursor->toArray());
+
         $this->assertArrayHasKey('n', $document);
         $this->assertEquals($count, $document['n']);
     }
 
-    protected function assertCommandSucceeded(Cursor $cursor)
+    protected function assertCommandSucceeded($document)
     {
-        $document = current($cursor->toArray());
+        if (is_object($document)) {
+            $document = get_object_vars($document);
+        }
+
         $this->assertArrayHasKey('ok', $document);
         $this->assertEquals(1, $document['ok']);
     }
@@ -42,6 +46,7 @@ protected function getServerVersion(ReadPreference $readPreference = null)
             $readPreference ?: new ReadPreference(ReadPreference::RP_PRIMARY)
         );
 
+        $cursor->setTypeMap(array('document' => 'array'));
         $document = current($cursor->toArray());
 
         return $document['version'];
diff --git a/tests/PedantryTest.php b/tests/PedantryTest.php
index 5ee136c62..f0f16361e 100644
--- a/tests/PedantryTest.php
+++ b/tests/PedantryTest.php
@@ -62,6 +62,10 @@ public function provideProjectClassNames()
         $files = new RegexIterator(new RecursiveIteratorIterator(new RecursiveDirectoryIterator($srcDir)), '/\.php$/i');
 
         foreach ($files as $file) {
+            if ($file->getFilename() === 'functions.php') {
+                continue;
+            }
+
             $classNames[][] = 'MongoDB\\' . str_replace(DIRECTORY_SEPARATOR, '\\', substr($file->getRealPath(), strlen($srcDir) + 1, -4));
         }