diff --git a/components/asset.rst b/components/asset.rst
index 20b5ce20b2d..48e51754449 100644
--- a/components/asset.rst
+++ b/components/asset.rst
@@ -200,12 +200,12 @@ every day::
             $this->version = date('Ymd');
         }
 
-        public function getVersion($path)
+        public function getVersion(string $path)
         {
             return $this->version;
         }
 
-        public function applyVersion($path)
+        public function applyVersion(string $path)
         {
             return sprintf('%s?v=%s', $path, $this->getVersion($path));
         }
diff --git a/configuration/env_var_processors.rst b/configuration/env_var_processors.rst
index b9782d270cd..464bf7af984 100644
--- a/configuration/env_var_processors.rst
+++ b/configuration/env_var_processors.rst
@@ -631,7 +631,7 @@ create a class that implements
 
     class LowercasingEnvVarProcessor implements EnvVarProcessorInterface
     {
-        public function getEnv($prefix, $name, \Closure $getEnv)
+        public function getEnv(string $prefix, string $name, \Closure $getEnv)
         {
             $env = $getEnv($name);
 
diff --git a/form/data_mappers.rst b/form/data_mappers.rst
index 15e66ce54b3..54081c09e47 100644
--- a/form/data_mappers.rst
+++ b/form/data_mappers.rst
@@ -98,7 +98,7 @@ in your form type::
         /**
          * @param Color|null $viewData
          */
-        public function mapDataToForms($viewData, $forms)
+        public function mapDataToForms($viewData, iterable $forms)
         {
             // there is no data yet, so nothing to prepopulate
             if (null === $viewData) {
@@ -119,7 +119,7 @@ in your form type::
             $forms['blue']->setData($viewData->getBlue());
         }
 
-        public function mapFormsToData($forms, &$viewData)
+        public function mapFormsToData(iterable $forms, &$viewData)
         {
             /** @var FormInterface[] $forms */
             $forms = iterator_to_array($forms);
diff --git a/form/type_guesser.rst b/form/type_guesser.rst
index f990aad4115..13f54999692 100644
--- a/form/type_guesser.rst
+++ b/form/type_guesser.rst
@@ -43,19 +43,19 @@ Start by creating the class and these methods. Next, you'll learn how to fill ea
 
     class PHPDocTypeGuesser implements FormTypeGuesserInterface
     {
-        public function guessType($class, $property)
+        public function guessType(string $class, string $property)
         {
         }
 
-        public function guessRequired($class, $property)
+        public function guessRequired(string $class, string $property)
         {
         }
 
-        public function guessMaxLength($class, $property)
+        public function guessMaxLength(string $class, string $property)
         {
         }
 
-        public function guessPattern($class, $property)
+        public function guessPattern(string $class, string $property)
         {
         }
     }
@@ -94,7 +94,7 @@ With this knowledge, you can implement the ``guessType()`` method of the
 
     class PHPDocTypeGuesser implements FormTypeGuesserInterface
     {
-        public function guessType($class, $property)
+        public function guessType(string $class, string $property)
         {
             $annotations = $this->readPhpDocAnnotations($class, $property);
 
@@ -129,7 +129,7 @@ With this knowledge, you can implement the ``guessType()`` method of the
             }
         }
 
-        protected function readPhpDocAnnotations($class, $property)
+        protected function readPhpDocAnnotations(string $class, string $property)
         {
             $reflectionProperty = new \ReflectionProperty($class, $property);
             $phpdoc = $reflectionProperty->getDocComment();
diff --git a/forms.rst b/forms.rst
index 5867d2f07d1..ec5a04fcfc1 100644
--- a/forms.rst
+++ b/forms.rst
@@ -672,7 +672,7 @@ Set the ``label`` option on fields to define their labels explicitly::
 
     ->add('dueDate', DateType::class, [
         // set it to FALSE to not display the label for this field
-        'label'  => 'To Be Completed Before',
+        'label' => 'To Be Completed Before',
     ])
 
 .. tip::
diff --git a/frontend/custom_version_strategy.rst b/frontend/custom_version_strategy.rst
index 6361ba632c0..0fe3f5ff987 100644
--- a/frontend/custom_version_strategy.rst
+++ b/frontend/custom_version_strategy.rst
@@ -71,13 +71,13 @@ version string::
          * @param string      $manifestPath
          * @param string|null $format
          */
-        public function __construct($manifestPath, $format = null)
+        public function __construct(string $manifestPath, string $format = null)
         {
             $this->manifestPath = $manifestPath;
             $this->format = $format ?: '%s?%s';
         }
 
-        public function getVersion($path)
+        public function getVersion(string $path)
         {
             if (!is_array($this->hashes)) {
                 $this->hashes = $this->loadManifest();
@@ -86,7 +86,7 @@ version string::
             return isset($this->hashes[$path]) ? $this->hashes[$path] : '';
         }
 
-        public function applyVersion($path)
+        public function applyVersion(string $path)
         {
             $version = $this->getVersion($path);
 
diff --git a/reference/dic_tags.rst b/reference/dic_tags.rst
index f7f43dca376..0aca3c91777 100644
--- a/reference/dic_tags.rst
+++ b/reference/dic_tags.rst
@@ -410,7 +410,7 @@ service class::
 
     class MyClearer implements CacheClearerInterface
     {
-        public function clear($cacheDirectory)
+        public function clear(string $cacheDirectory)
         {
             // clear your cache
         }
@@ -1062,7 +1062,7 @@ required option: ``alias``, which defines the name of the extractor::
         /**
          * Sets the prefix that should be used for new found messages.
          */
-        public function setPrefix($prefix)
+        public function setPrefix(string $prefix)
         {
             $this->prefix = $prefix;
         }
diff --git a/security/access_control.rst b/security/access_control.rst
index 9b345b87a24..b02b9057424 100644
--- a/security/access_control.rst
+++ b/security/access_control.rst
@@ -92,7 +92,7 @@ Take the following ``access_control`` entries as an example:
                     'path' => '^/admin',
                     'roles' => 'ROLE_USER_METHOD',
                     'methods' => 'POST, PUT',
-                ]
+                ],
             ],
         ]);
 
diff --git a/security/custom_authentication_provider.rst b/security/custom_authentication_provider.rst
index 3199128b26a..4a0a5be4407 100644
--- a/security/custom_authentication_provider.rst
+++ b/security/custom_authentication_provider.rst
@@ -410,7 +410,7 @@ to service ids that may not exist yet: ``App\Security\Authentication\Provider\Ws
 
             <services>
                 <service id="App\Security\Authentication\Provider\WsseProvider">
-                    <argument key="$cachePool" type="service" id="cache.app"></argument>
+                    <argument key="$cachePool" type="service" id="cache.app"/>
                 </service>
 
                 <service id="App\Security\Firewall\WsseListener">
diff --git a/security/user_provider.rst b/security/user_provider.rst
index 000a7a49a38..5fcf19f3bf2 100644
--- a/security/user_provider.rst
+++ b/security/user_provider.rst
@@ -135,7 +135,7 @@ interface only requires one method: ``loadUserByUsername($username)``::
     {
         // ...
 
-        public function loadUserByUsername($usernameOrEmail)
+        public function loadUserByUsername(string $usernameOrEmail)
         {
             $entityManager = $this->getEntityManager();
             
@@ -376,7 +376,7 @@ command will generate a nice skeleton to get you started::
          *
          * @throws UsernameNotFoundException if the user is not found
          */
-        public function loadUserByUsername($username)
+        public function loadUserByUsername(string $username)
         {
             // Load a User object from your data source or throw UsernameNotFoundException.
             // The $username argument may not actually be a username:
@@ -412,7 +412,7 @@ command will generate a nice skeleton to get you started::
         /**
          * Tells Symfony to use this provider for this User class.
          */
-        public function supportsClass($class)
+        public function supportsClass(string $class)
         {
             return User::class === $class || is_subclass_of($class, User::class);
         }
diff --git a/serializer/custom_encoders.rst b/serializer/custom_encoders.rst
index 5bb78def4e4..e6bae859336 100644
--- a/serializer/custom_encoders.rst
+++ b/serializer/custom_encoders.rst
@@ -27,22 +27,22 @@ create your own encoder that uses the
 
     class YamlEncoder implements EncoderInterface, DecoderInterface
     {
-        public function encode($data, $format, array $context = [])
+        public function encode($data, string $format, array $context = [])
         {
             return Yaml::dump($data);
         }
 
-        public function supportsEncoding($format)
+        public function supportsEncoding(string $format)
         {
             return 'yaml' === $format;
         }
 
-        public function decode($data, $format, array $context = [])
+        public function decode(string $data, string $format, array $context = [])
         {
             return Yaml::parse($data);
         }
 
-        public function supportsDecoding($format)
+        public function supportsDecoding(string $format)
         {
             return 'yaml' === $format;
         }
diff --git a/session/locale_sticky_session.rst b/session/locale_sticky_session.rst
index f8caef23370..056f2a674cb 100644
--- a/session/locale_sticky_session.rst
+++ b/session/locale_sticky_session.rst
@@ -28,7 +28,7 @@ correct locale however you want::
     {
         private $defaultLocale;
 
-        public function __construct($defaultLocale = 'en')
+        public function __construct(string $defaultLocale = 'en')
         {
             $this->defaultLocale = $defaultLocale;
         }