# Class yii\filters\ContentNegotiator

Inheritance | yii\filters\ContentNegotiator » yii\base\ActionFilter » yii\base\Behavior » yii\base\BaseObject
Implements | yii\base\BootstrapInterface, yii\base\Configurable
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/filters/ContentNegotiator.php

ContentNegotiator supports response format negotiation and application language negotiation.

When the supported formats property is specified, ContentNegotiator will support response format negotiation based on the value of the GET parameter $formatParam and the `Accept` HTTP header. If a match is found, the yii\web\Response::$format property will be set as the chosen format. The yii\web\Response::$acceptMimeType as well as yii\web\Response::$acceptParams will also be updated accordingly.

When the supported languages is specified, ContentNegotiator will support application language negotiation based on the value of the GET parameter $languageParam and the `Accept-Language` HTTP header. If a match is found, the yii\base\Application::$language property will be set as the chosen language.

You may use ContentNegotiator as a bootstrapping component as well as an action filter.

The following code shows how you can use ContentNegotiator as a bootstrapping component. Note that in this case, the content negotiation applies to the whole application.

    // in application configuration
    use yii\web\Response;

    return [
        'bootstrap' => [
            [
                'class' => 'yii\filters\ContentNegotiator',
                'formats' => [
                    'application/json' => Response::FORMAT_JSON,
                    'application/xml' => Response::FORMAT_XML,
                ],
                'languages' => [
                    'en',
                    'de',
                ],
            ],
        ],
    ];

The following code shows how you can use ContentNegotiator as an action filter in either a controller or a module. In this case, the content negotiation result only applies to the corresponding controller or module, or even specific actions if you configure the `only` or `except` property of the filter.

    use yii\web\Response;

    public function behaviors()
    {
        return [
            [
                'class' => 'yii\filters\ContentNegotiator',
                'only' => ['view', 'index'],  // in a controller
                // if in a module, use the following IDs for user actions
                // 'only' => ['user/view', 'user/index']
                'formats' => [
                    'application/json' => Response::FORMAT_JSON,
                ],
                'languages' => [
                    'en',
                    'de',
                ],
            ],
        ];
    }

## Public Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$except | array | List of action IDs that this filter should not apply to. | yii\base\ActionFilter
$formatParam | string | The name of the GET parameter that specifies the response format. | yii\filters\ContentNegotiator
$formats | array|null | List of supported response formats. | yii\filters\ContentNegotiator
$languageParam | string | The name of the GET parameter that specifies the application language. | yii\filters\ContentNegotiator
$languages | array|null | A list of supported languages. | yii\filters\ContentNegotiator
$only | array | List of action IDs that this filter should apply to. | yii\base\ActionFilter
$owner | yii\base\Component|null | The owner of this behavior | yii\base\Behavior
$request | yii\web\Request | The current request. | yii\filters\ContentNegotiator
$response | yii\web\Response|null | The response to be sent. | yii\filters\ContentNegotiator

## Public Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
__call() | Calls the named method which is not a class method. | yii\base\BaseObject
__construct() | Constructor. | yii\base\BaseObject
__get() | Returns the value of an object property. | yii\base\BaseObject
__isset() | Checks if a property is set, i.e. defined and not null. | yii\base\BaseObject
__set() | Sets value of an object property. | yii\base\BaseObject
__unset() | Sets an object property to null. | yii\base\BaseObject
afterAction() | This method is invoked right after an action is executed. | yii\base\ActionFilter
afterFilter() |  | yii\base\ActionFilter
attach() | Attaches the behavior object to the component. | yii\base\ActionFilter
beforeAction() | This method is invoked right before an action is to be executed (after all possible filters.) You may override this method to do last-minute preparation for the action. | yii\filters\ContentNegotiator
beforeFilter() |  | yii\base\ActionFilter
bootstrap() | Bootstrap method to be called during application bootstrap stage. | yii\filters\ContentNegotiator
canGetProperty() | Returns a value indicating whether a property can be read. | yii\base\BaseObject
canSetProperty() | Returns a value indicating whether a property can be set. | yii\base\BaseObject
className() | Returns the fully qualified name of this class. | yii\base\BaseObject
detach() | Detaches the behavior object from the component. | yii\base\ActionFilter
events() | Declares event handlers for the $owner's events. | yii\base\Behavior
hasMethod() | Returns a value indicating whether a method is defined. | yii\base\BaseObject
hasProperty() | Returns a value indicating whether a property is defined. | yii\base\BaseObject
init() | Initializes the object. | yii\base\BaseObject
negotiate() | Negotiates the response format and application language. | yii\filters\ContentNegotiator

## Protected Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
getActionId() | Returns an action ID by converting yii\base\Action::$uniqueId into an ID relative to the module. | yii\base\ActionFilter
isActive() | Returns a value indicating whether the filter is active for the given action. | yii\base\ActionFilter
isLanguageSupported() | Returns a value indicating whether the requested language matches the supported language. | yii\filters\ContentNegotiator
negotiateContentType() | Negotiates the response format. | yii\filters\ContentNegotiator
negotiateLanguage() | Negotiates the application language. | yii\filters\ContentNegotiator

## Property Details

Hide inherited properties

$formatParam public property

The name of the GET parameter that specifies the response format. Note that if the specified format does not exist in $formats, a yii\web\NotAcceptableHttpException exception will be thrown. If the parameter value is empty or if this property is null, the response format will be determined based on the `Accept` HTTP header only.

See also $formats.

public string $formatParam = '_format'
$formats public property

List of supported response formats. The keys are MIME types (e.g. `application/json`) while the values are the corresponding formats (e.g. `html`, `json`) which must be supported as declared in yii\web\Response::$formatters.

If this property is empty or not set, response format negotiation will be skipped.

public array|null $formats = null
$languageParam public property

The name of the GET parameter that specifies the application language. Note that if the specified language does not match any of $languages, the first language in $languages will be used. If the parameter value is empty or if this property is null, the application language will be determined based on the `Accept-Language` HTTP header only.

See also $languages.

public string $languageParam = '_lang'
$languages public property

A list of supported languages. The array keys are the supported language variants (e.g. `en-GB`, `en-US`), while the array values are the corresponding language codes (e.g. `en`, `de`) recognized by the application.

Array keys are not always required. When an array value does not have a key, the matching of the requested language will be based on a language fallback mechanism. For example, a value of `en` will match `en`, `en_US`, `en-US`, `en-GB`, etc.

If this property is empty or not set, language negotiation will be skipped.

public array|null $languages = null
$request public property

The current request. If not set, the `request` application component will be used.

public yii\web\Request $request = null
$response public property

The response to be sent. If not set, the `response` application component will be used.

public yii\web\Response|null $response = null

## Method Details

Hide inherited methods

__call() public method

Defined in: yii\base\BaseObject::__call()

Calls the named method which is not a class method.

Do not call this method directly as it is a PHP magic method that will be implicitly called when an unknown method is being invoked.

public mixed __call ( $name, $params )
$name | string | The method name
$params | array | Method parameters
return | mixed | The method return value
throws | yii\base\UnknownMethodException | when calling unknown method

Source code

                    public function __call($name, $params)
    {
        throw new UnknownMethodException('Calling unknown method: ' . get_class($this) . "::$name()");
    }

__construct() public method

Defined in: yii\base\BaseObject::__construct()

Constructor.

The default implementation does two things:

- Initializes the object with the given configuration `$config`.
- Call init().

If this method is overridden in a child class, it is recommended that

- the last parameter of the constructor is a configuration array, like `$config` here.
- call the parent implementation at the end of the constructor.

public void __construct ( $config = [] )
$config | array | Name-value pairs that will be used to initialize the object properties

Source code

                    public function __construct($config = [])
    {
        if (!empty($config)) {
            Yii::configure($this, $config);
        }
        $this->init();
    }

__get() public method

Defined in: yii\base\BaseObject::__get()

Returns the value of an object property.

Do not call this method directly as it is a PHP magic method that will be implicitly called when executing `$value = $object->property;`.

See also __set().

public mixed __get ( $name )
$name | string | The property name
return | mixed | The property value
throws | yii\base\UnknownPropertyException | if the property is not defined
throws | yii\base\InvalidCallException | if the property is write-only

Source code

                    public function __get($name)
    {
        $getter = 'get' . $name;
        if (method_exists($this, $getter)) {
            return $this->$getter();
        } elseif (method_exists($this, 'set' . $name)) {
            throw new InvalidCallException('Getting write-only property: ' . get_class($this) . '::' . $name);
        }
        throw new UnknownPropertyException('Getting unknown property: ' . get_class($this) . '::' . $name);
    }

__isset() public method

Defined in: yii\base\BaseObject::__isset()

Checks if a property is set, i.e. defined and not null.

Do not call this method directly as it is a PHP magic method that will be implicitly called when executing `isset($object->property)`.

Note that if the property is not defined, false will be returned.

See also https://www.php.net/manual/en/function.isset.php.

public boolean __isset ( $name )
$name | string | The property name or the event name
return | boolean | Whether the named property is set (not null).

Source code

                    public function __isset($name)
    {
        $getter = 'get' . $name;
        if (method_exists($this, $getter)) {
            return $this->$getter() !== null;
        }
        return false;
    }

__set() public method

Defined in: yii\base\BaseObject::__set()

Sets value of an object property.

Do not call this method directly as it is a PHP magic method that will be implicitly called when executing `$object->property = $value;`.

See also __get().

public void __set ( $name, $value )
$name | string | The property name or the event name
$value | mixed | The property value
throws | yii\base\UnknownPropertyException | if the property is not defined
throws | yii\base\InvalidCallException | if the property is read-only

Source code

                    public function __set($name, $value)
    {
        $setter = 'set' . $name;
        if (method_exists($this, $setter)) {
            $this->$setter($value);
        } elseif (method_exists($this, 'get' . $name)) {
            throw new InvalidCallException('Setting read-only property: ' . get_class($this) . '::' . $name);
        } else {
            throw new UnknownPropertyException('Setting unknown property: ' . get_class($this) . '::' . $name);
        }
    }

__unset() public method

Defined in: yii\base\BaseObject::__unset()

Sets an object property to null.

Do not call this method directly as it is a PHP magic method that will be implicitly called when executing `unset($object->property)`.

Note that if the property is not defined, this method will do nothing. If the property is read-only, it will throw an exception.

See also https://www.php.net/manual/en/function.unset.php.

public void __unset ( $name )
$name | string | The property name
throws | yii\base\InvalidCallException | if the property is read only.

Source code

                    public function __unset($name)
    {
        $setter = 'set' . $name;
        if (method_exists($this, $setter)) {
            $this->$setter(null);
        } elseif (method_exists($this, 'get' . $name)) {
            throw new InvalidCallException('Unsetting read-only property: ' . get_class($this) . '::' . $name);
        }
    }

afterAction() public method

Defined in: yii\base\ActionFilter::afterAction()

This method is invoked right after an action is executed.

You may override this method to do some postprocessing for the action.

public mixed afterAction ( $action, $result )
$action | yii\base\Action | The action just executed.
$result | mixed | The action execution result
return | mixed | The processed action result.

Source code

                    public function afterAction($action, $result)
    {
        return $result;
    }

afterFilter() public method

Defined in: yii\base\ActionFilter::afterFilter()

public void afterFilter ( $event )
$event | yii\base\ActionEvent |

Source code

                    public function afterFilter($event)
    {
        $event->result = $this->afterAction($event->action, $event->result);
        $this->owner->off(Controller::EVENT_AFTER_ACTION, [$this, 'afterFilter']);
    }

attach() public method

Defined in: yii\base\ActionFilter::attach()

Attaches the behavior object to the component.

The default implementation will set the $owner property and attach event handlers as declared in events(). Make sure you call the parent implementation if you override this method.

public void attach ( $owner )
$owner | yii\base\Component | The component that this behavior is to be attached to.

Source code

                    public function attach($owner)
    {
        $this->owner = $owner;
        $owner->on(Controller::EVENT_BEFORE_ACTION, [$this, 'beforeFilter']);
    }

beforeAction() public method

This method is invoked right before an action is to be executed (after all possible filters.) You may override this method to do last-minute preparation for the action.

public boolean beforeAction ( $action )
$action | yii\base\Action | The action to be executed.
return | boolean | Whether the action should continue to be executed.

Source code

                    public function beforeAction($action)
    {
        $this->negotiate();
        return true;
    }

beforeFilter() public method

Defined in: yii\base\ActionFilter::beforeFilter()

public void beforeFilter ( $event )
$event | yii\base\ActionEvent |

Source code

                    public function beforeFilter($event)
    {
        if (!$this->isActive($event->action)) {
            return;
        }
        $event->isValid = $this->beforeAction($event->action);
        if ($event->isValid) {
            // call afterFilter only if beforeFilter succeeds
            // beforeFilter and afterFilter should be properly nested
            $this->owner->on(Controller::EVENT_AFTER_ACTION, [$this, 'afterFilter'], null, false);
        } else {
            $event->handled = true;
        }
    }

bootstrap() public method

Bootstrap method to be called during application bootstrap stage.

public void bootstrap ( $app )
$app | yii\base\Application | The application currently running

Source code

                    public function bootstrap($app)
    {
        $this->negotiate();
    }

canGetProperty() public method

Defined in: yii\base\BaseObject::canGetProperty()

Returns a value indicating whether a property can be read.

A property is readable if:

- the class has a getter method associated with the specified name (in this case, property name is case-insensitive);
- the class has a member variable with the specified name (when `$checkVars` is true);

See also canSetProperty().

public boolean canGetProperty ( $name, $checkVars = true )
$name | string | The property name
$checkVars | boolean | Whether to treat member variables as properties
return | boolean | Whether the property can be read

Source code

                    public function canGetProperty($name, $checkVars = true)
    {
        return method_exists($this, 'get' . $name) || $checkVars && property_exists($this, $name);
    }

canSetProperty() public method

Defined in: yii\base\BaseObject::canSetProperty()

Returns a value indicating whether a property can be set.

A property is writable if:

- the class has a setter method associated with the specified name (in this case, property name is case-insensitive);
- the class has a member variable with the specified name (when `$checkVars` is true);

See also canGetProperty().

public boolean canSetProperty ( $name, $checkVars = true )
$name | string | The property name
$checkVars | boolean | Whether to treat member variables as properties
return | boolean | Whether the property can be written

Source code

                    public function canSetProperty($name, $checkVars = true)
    {
        return method_exists($this, 'set' . $name) || $checkVars && property_exists($this, $name);
    }

className() public static method
Deprecated since 2.0.14. On PHP >=5.5, use `::class` instead.

Defined in: yii\base\BaseObject::className()

Returns the fully qualified name of this class.

public static string className ( )
return | string | The fully qualified name of this class.

Source code

                    public static function className()
    {
        return get_called_class();
    }

detach() public method

Defined in: yii\base\ActionFilter::detach()

Detaches the behavior object from the component.

The default implementation will unset the $owner property and detach event handlers declared in events(). Make sure you call the parent implementation if you override this method.

public void detach ( )

Source code

                    public function detach()
    {
        if ($this->owner) {
            $this->owner->off(Controller::EVENT_BEFORE_ACTION, [$this, 'beforeFilter']);
            $this->owner->off(Controller::EVENT_AFTER_ACTION, [$this, 'afterFilter']);
            $this->owner = null;
        }
    }

events() public method

Defined in: yii\base\Behavior::events()

Declares event handlers for the $owner's events.

Child classes may override this method to declare what PHP callbacks should be attached to the events of the $owner component.

The callbacks will be attached to the $owner's events when the behavior is attached to the owner; and they will be detached from the events when the behavior is detached from the component.

The callbacks can be any of the following:

- method in this behavior: `'handleClick'`, equivalent to `[$this, 'handleClick']`
- object method: `[$object, 'handleClick']`
- static method: `['Page', 'handleClick']`
- anonymous function: `function ($event) { ... }`

The following is an example:

    [
        Model::EVENT_BEFORE_VALIDATE => 'myBeforeValidate',
        Model::EVENT_AFTER_VALIDATE => 'myAfterValidate',
    ]

public array events ( )
return | array | Events (array keys) and the corresponding event handler methods (array values).

Source code

                    public function events()
    {
        return [];
    }

getActionId() protected method (available since version 2.0.7)

Defined in: yii\base\ActionFilter::getActionId()

Returns an action ID by converting yii\base\Action::$uniqueId into an ID relative to the module.

protected string getActionId ( $action )
$action | yii\base\Action |

Source code

                    protected function getActionId($action)
    {
        if ($this->owner instanceof Module) {
            $mid = $this->owner->getUniqueId();
            $id = $action->getUniqueId();
            if ($mid !== '' && strpos($id, $mid) === 0) {
                $id = substr($id, strlen($mid) + 1);
            }
        } else {
            $id = $action->id;
        }
        return $id;
    }

hasMethod() public method

Defined in: yii\base\BaseObject::hasMethod()

Returns a value indicating whether a method is defined.

The default implementation is a call to php function `method_exists()`. You may override this method when you implemented the php magic method `__call()`.

public boolean hasMethod ( $name )
$name | string | The method name
return | boolean | Whether the method is defined

Source code

                    public function hasMethod($name)
    {
        return method_exists($this, $name);
    }

hasProperty() public method

Defined in: yii\base\BaseObject::hasProperty()

Returns a value indicating whether a property is defined.

A property is defined if:

- the class has a getter or setter method associated with the specified name (in this case, property name is case-insensitive);
- the class has a member variable with the specified name (when `$checkVars` is true);

See also:

- canGetProperty()
- canSetProperty()

public boolean hasProperty ( $name, $checkVars = true )
$name | string | The property name
$checkVars | boolean | Whether to treat member variables as properties
return | boolean | Whether the property is defined

Source code

                    public function hasProperty($name, $checkVars = true)
    {
        return $this->canGetProperty($name, $checkVars) || $this->canSetProperty($name, false);
    }

init() public method

Defined in: yii\base\BaseObject::init()

Initializes the object.

This method is invoked at the end of the constructor after the object is initialized with the given configuration.

public void init ( )

Source code

                    public function init()
    {
    }

isActive() protected method

Defined in: yii\base\ActionFilter::isActive()

Returns a value indicating whether the filter is active for the given action.

protected boolean isActive ( $action )
$action | yii\base\Action | The action being filtered
return | boolean | Whether the filter is active for the given action.

Source code

                    protected function isActive($action)
    {
        $id = $this->getActionId($action);
        if (empty($this->only)) {
            $onlyMatch = true;
        } else {
            $onlyMatch = false;
            foreach ($this->only as $pattern) {
                if (StringHelper::matchWildcard($pattern, $id)) {
                    $onlyMatch = true;
                    break;
                }
            }
        }
        $exceptMatch = false;
        foreach ($this->except as $pattern) {
            if (StringHelper::matchWildcard($pattern, $id)) {
                $exceptMatch = true;
                break;
            }
        }
        return !$exceptMatch && $onlyMatch;
    }

isLanguageSupported() protected method

Returns a value indicating whether the requested language matches the supported language.

protected boolean isLanguageSupported ( $requested, $supported )
$requested | string | The requested language code
$supported | string | The supported language code
return | boolean | Whether the requested language is supported

Source code

                    protected function isLanguageSupported($requested, $supported)
    {
        $supported = str_replace('_', '-', strtolower($supported));
        $requested = str_replace('_', '-', strtolower($requested));
        return strpos($requested . '-', $supported . '-') === 0;
    }

negotiate() public method

Negotiates the response format and application language.

public void negotiate ( )

Source code

                    public function negotiate()
    {
        $request = $this->request ?: Yii::$app->getRequest();
        $response = $this->response ?: Yii::$app->getResponse();
        if (!empty($this->formats)) {
            if (\count($this->formats) > 1) {
                $response->getHeaders()->add('Vary', 'Accept');
            }
            $this->negotiateContentType($request, $response);
        }
        if (!empty($this->languages)) {
            if (\count($this->languages) > 1) {
                $response->getHeaders()->add('Vary', 'Accept-Language');
            }
            Yii::$app->language = $this->negotiateLanguage($request);
        }
    }

negotiateContentType() protected method

Negotiates the response format.

protected void negotiateContentType ( $request, $response )
$request | yii\web\Request |
$response | yii\web\Response |
throws | yii\web\BadRequestHttpException | if an array received for GET parameter $formatParam.
throws | yii\web\NotAcceptableHttpException | if none of the requested content types is accepted.

Source code

                    protected function negotiateContentType($request, $response)
    {
        if (!empty($this->formatParam) && ($format = $request->get($this->formatParam)) !== null) {
            if (is_array($format)) {
                throw new BadRequestHttpException("Invalid data received for GET parameter '{$this->formatParam}'.");
            }
            if (in_array($format, $this->formats)) {
                $response->format = $format;
                $response->acceptMimeType = null;
                $response->acceptParams = [];
                return;
            }
            throw new NotAcceptableHttpException('The requested response format is not supported: ' . $format);
        }
        $types = $request->getAcceptableContentTypes();
        if (empty($types)) {
            $types['*/*'] = [];
        }
        foreach ($types as $type => $params) {
            if (isset($this->formats[$type])) {
                $response->format = $this->formats[$type];
                $response->acceptMimeType = $type;
                $response->acceptParams = $params;
                return;
            }
        }
        foreach ($this->formats as $type => $format) {
            $response->format = $format;
            $response->acceptMimeType = $type;
            $response->acceptParams = [];
            break;
        }
        if (isset($types['*/*'])) {
            return;
        }
        throw new NotAcceptableHttpException('None of your requested content types is supported.');
    }

negotiateLanguage() protected method

Negotiates the application language.

protected string negotiateLanguage ( $request )
$request | yii\web\Request |
return | string | The chosen language

Source code

                    protected function negotiateLanguage($request)
    {
        if (!empty($this->languageParam) && ($language = $request->get($this->languageParam)) !== null) {
            if (is_array($language)) {
                // If an array received, then skip it and use the first of supported languages
                return reset($this->languages);
            }
            if (isset($this->languages[$language])) {
                return $this->languages[$language];
            }
            foreach ($this->languages as $key => $supported) {
                if (is_int($key) && $this->isLanguageSupported($language, $supported)) {
                    return $supported;
                }
            }
            return reset($this->languages);
        }
        foreach ($request->getAcceptableLanguages() as $language) {
            if (isset($this->languages[$language])) {
                return $this->languages[$language];
            }
            foreach ($this->languages as $key => $supported) {
                if (is_int($key) && $this->isLanguageSupported($language, $supported)) {
                    return $supported;
                }
            }
        }
        return reset($this->languages);
    }