What is the alternative for Fatal error: Uncaught Error: Call to undefined method MongoDB\Driver\Cursor::hasNext?

[ziyaindia]

What is the alternative for Fatal error: Uncaught Error: Call to undefined method MongoDB\Driver\Cursor::hasNext?

One of my application using MongoDB Client library with old php version. I just upgraded my php version as well as upgraded mongo library. When following function is calling, it's giving me

Fatal error: Uncaught Error: Call to undefined method MongoDB\Driver\Cursor::hasNext

`function get_result_row () {

    if ($this->cursor->hasNext()) {
        return $this->cursor->getNext();
    }

}`

Please suggest how i can fix it?

[jmikola]

One of my application using MongoDB Client library with old php version. I just upgraded my php version as well as upgraded mongo library.

I assume your application was previously using the legacy mongo extension. The MongoDB library (this repository) has always required the mongodb extension.

The legacy driver's MongoCursor::hasNext() has not direct equivalent in the current extension and library. That method would previously return true if there was either a yet-to-be-iterated document immediately available in the client's current batch of results for the cursor, or, if the current batch had been exhausted, the method would issue a getMore command to fetch the next batch and make a determination using that server response (and also update the cursor's local batch).

In the current driver, there is a MongoDB\Driver\Cursor::isDead() that returns true if the cursor definitively has no more results; however, a false return value means that the cursor may or may not have more results. The documentation explains the justification for this design, and why we cannot definitively say that a cursor has more results.

That said, it is possible to implement the old driver's hasNext() logic by wrapping a MongoDB\Driver\Cursor with your own iterator and implement logic to peak at the next element. The Tailable Cursor Iteration tutorial in the library docs discusses how to wrap cursors (both regular and tailable types) using PHP's IteratorIterator class. A real-world example of this in practice would be the MongoCursor::hasNext() method from the alcaeus/mongo-php-adapter package, which is a separate library that implements the original mongo API on top of the current extension and library.

[ziyaindia]

The Tailable Cursor Iteration is not working with a collection that is the result of executeQuery. How I can coded it with find method?

function searchQuery($collection, $limit, $filter = array(), $field = array()) {

            if($limit > 0) {
                $options = array(
                    "sort" => array("timestamp" => -1),
                    "limit"=> $limit
                );
            } else {
                $options = array(
                    "sort" => array("timestamp" => -1)
                );
            }
            
            $query = $this->get_dbquery($filter, $options);

            $this->cursor = $this->manager->executeQuery("$this->dbf.$collection", $query);

        }

[ziyaindia]

Can I use MongoClient with php 7?

[jmikola]

The Tailable Cursor Iteration is not working with a collection that is the result of executeQuery.

The following example demonstrates that IteratorIterator can wrap a MongoDB\Driver\Cursor object.

<?php

require_once 'vendor/autoload.php';

$client = new MongoDB\Client('mongodb://localhost:27017');

$collection = $client->test->foo;
$collection->drop();

$collection->insertMany([
    ['x' => 1],
    ['x' => 2],
]);

$cursor = $collection->find();

$iterator = new IteratorIterator($cursor);

$iterator->rewind();
var_dump($iterator->current());
$iterator->next();
var_dump($iterator->current());

In this case, I'm using the library's API to be more concise, but the returned MongoDB\Driver\Cursor would be the same if you called the extension's MongoDB\Driver\Manager::executeQuery() method directly. If you look at the library's source for the Find operation you'll see that it calls executeQuery() internally.

I'll also point out that in the example above there is no benefit to wrapping the cursor with IteratorIterator, since a normal query cursor can be iterated with foreach. Wrapping a cursor with IteratorIterator is really only useful in two cases:

• Iterating tailable cursors, since foreach would stop immediately as soon as a document is not available -- and tailable cursors may still be able to return more results by manually iterating even if there is not one currently available.
• If you want direct control over iteration of any type of cursor to implement extra functionality, such as a hasNext() method, which you were asking about in your original post.

Can I use MongoClient with php 7?

The MongoClient class is from the legacy mongo extension, which is not compatible with PHP 7. My last comment referred to the alcaeus/mongo-php-adapter package, which implements the mongo extension API using the newer mongodb extension, which does support PHP 7. That package be the only way to use the old driver's API with PHP 7; however, any new application would be better off using the current driver (i.e. mongodb extension and the library in this repository) directly rather than the adapter library.

[ziyaindia]

Thanks A Lot jmikola
Happy New Year Dear

When I am trying to connect mongo with my below old code:

function connect($username,$password,$hostname,$port, $dbname)
        {
            //$this->serverString = "mongodb://".$hostname.":".$port;

            $this->serverString = "mongodb://".$username.":".$password."@".$hostname.":".$port;
            //$userDetails = array('username' => $username, 'password' => $password);
            //$this->client = new MongoClient($this->serverString, $userDetails);
            //die;
            try {
                $this->client = new MongoClient($this->serverString);
            } catch (Exception $e) {
                die('MongoDB NOT WORKING ERROR CODE '.$e->getCode().' ERROR MESSAGE '.$e->getMessage());
            }

            $this->uname = $username;
            $this->pass = $password;
            $this->dbf = $dbname;

            return $this->client;
        }// function Connect

It's giving me MongoClient is not exist. I used following way to connect mongo.

Is it correct way to connect?

function connect($username,$password,$hostname,$port, $dbname) {

            $this->serverString = "mongodb://".$username.":".$password."@".$hostname.":".$port."/".$this->dbf;

            try {
                $this->manager = new \MongoDB\Driver\Manager($this->serverString, array("connectTimeoutMS" => MONGO_CURSOR_TIMEOUT));
            } catch (Exception $e) {
                die('MongoDB NOT WORKING ERROR CODE '.$e->getCode().' ERROR MESSAGE '.$e->getMessage());
            }

            $this->uname = $username;
            $this->pass = $password;
            $this->dbf = $dbname;

            return $this->manager;
        }

Please suggest
Thanks in Advance
Ziya

[jmikola]

The code in your second example is correct for the mongodb extension. I would suggest you read through the docs for MongoDB\Driver\Manager and its constructor method. You can compare that with the old documentation for the mongo extension's MongoClient class.

If you are using the mongodb extension directly, most of the documentation pages for its classes and methods (on PHP.net) should have usage examples. However, you would be better off using the extension with the library, since its API is much more convenient and more closely resembles the legacy mongo extension's API you're already familiar with. The library documentation is available through https://docs.mongodb.com/php-library/current/ and there are more tutorial articles available than you'll find on the mongodb docs (which are mostly just API documentation). Additionally, the library has an Upgrade Guide that covers most of the differences from the mongo extension -- mainly pertaining to how the new driver converts BSON documents to PHP values and the library's Collection API.

[ziyaindia]

Thanks for your reply
I need to check my script as you suggested.
In between
I am facing new issue in Compiling C++ with new MongoDB Driver

Do you have any idea about that?

[jmikola]

I am facing new issue in Compiling C++ with new MongoDB Driver

One of the Community Support Resources would be a better forum for questions on that. If you're actually encountering a bug with the C++ driver, you can report an issue in the CXX project within MongoDB's JIRA, but JIRA should not be used for general support questions.

[alcaeus]

Closing due to inactivity. Feel free to follow up if this is still outstanding.

[ziyaindia]

Hi Jmikola,

Following code is not working for me:

`function get_result_row () {

        if (!$this->cursor->isDead()) {
            return $this->cursor->next();
        }
        return false;
    }`

Fatal error: Uncaught Error: Call to undefined method MongoDB\Driver\Cursor::next()