Symfony Framework Events
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Symfony Framework Events
When the Symfony Framework (or anything using the HttpKernel) handles a request, a few core events are dispatched so that you can add listeners throughout the process. These are called the "kernel events". For a larger explanation, see The HttpKernel Component.
Kernel Events
Each event dispatched by the kernel is a subclass of KernelEvent. This means that each event has access to the following information:
- getRequestType()
-
Returns the type of the request (
HttpKernelInterface::MASTER_REQUEST
orHttpKernelInterface::SUB_REQUEST
). - getKernel()
- Returns the Kernel handling the request.
- getRequest()
-
Returns the current
Request
being handled.
kernel.request
Event Class: GetResponseEvent
This event is dispatched very early in Symfony, before the controller is determined.
See also
Read more on the kernel.request event.
These are the built-in Symfony listeners registered to this event:
Listener Class Name | Priority |
---|---|
ProfilerListener | 1024 |
TestSessionListener | 192 |
SessionListener | 128 |
RouterListener | 32 |
LocaleListener | 16 |
Firewall | 8 |
kernel.controller
Event Class: FilterControllerEvent
This event can be an entry point used to modify the controller that should be executed:
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use Symfony\Component\HttpKernel\Event\FilterControllerEvent;
public function onKernelController(FilterControllerEvent $event)
{
$controller = $event->getController();
// ...
// the controller can be changed to any PHP callable
$event->setController($controller);
}
See also
Read more on the kernel.controller event.
This is the built-in Symfony listener related to this event:
Listener Class Name | Priority |
---|---|
RequestDataCollector | 0 |
kernel.view
Event Class: GetResponseForControllerResultEvent
This event is not used by the FrameworkBundle, but it can be used to implement
a view sub-system. This event is called only if the Controller does not
return a Response
object. The purpose of the event is to allow some
other return value to be converted into a Response
.
The value returned by the Controller is accessible via the getControllerResult
method:
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use Symfony\Component\HttpKernel\Event\GetResponseForControllerResultEvent;
use Symfony\Component\HttpFoundation\Response;
public function onKernelView(GetResponseForControllerResultEvent $event)
{
$val = $event->getControllerResult();
$response = new Response();
// ... somehow customize the Response from the return value
$event->setResponse($response);
}
See also
Read more on the kernel.view event.
kernel.response
Event Class: FilterResponseEvent
The purpose of this event is to allow other systems to modify or replace
the Response
object after its creation:
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public function onKernelResponse(FilterResponseEvent $event)
{
$response = $event->getResponse();
// ... modify the response object
}
The FrameworkBundle registers several listeners:
- ProfilerListener
- Collects data for the current request.
- WebDebugToolbarListener
- Injects the Web Debug Toolbar.
- ResponseListener
-
Fixes the Response
Content-Type
based on the request format. - EsiListener
-
Adds a
Surrogate-Control
HTTP header when the Response needs to be parsed for ESI tags.
See also
Read more on the kernel.response event.
These are the built-in Symfony listeners registered to this event:
Listener Class Name | Priority |
---|---|
EsiListener | 0 |
ResponseListener | 0 |
ResponseListener | 0 |
ProfilerListener | -100 |
TestSessionListener | -128 |
WebDebugToolbarListener | -128 |
StreamedResponseListener | -1024 |
kernel.finish_request
Event Class: FinishRequestEvent
The purpose of this event is to allow you to reset the global and environmental state of the application after a sub-request has finished (for example, the translator listener resets the translator's locale to the one of the parent request):
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public function onKernelFinishRequest(FinishRequestEvent $event)
{
if (null === $parentRequest = $this->requestStack->getParentRequest()) {
return;
}
//Reset the locale of the subrequest to the locale of the parent request
$this->setLocale($parentRequest);
}
These are the built-in Symfony listeners related to this event:
Listener Class Name | Priority |
---|---|
LocaleListener | 0 |
TranslatorListener | 0 |
RouterListener | 0 |
Firewall | 0 |
kernel.terminate
Event Class: PostResponseEvent
The purpose of this event is to perform tasks after the response was already served to the client.
See also
Read more on the kernel.terminate event.
This is the built-in Symfony listener related to this event:
Listener Class Name | Priority |
---|---|
EmailSenderListener | 0 |
kernel.exception
Event Class: GetResponseForExceptionEvent
The TwigBundle registers an ExceptionListener
that forwards the Request
to a given controller defined by the
exception_listener.controller
parameter.
A listener on this event can create and set a Response
object, create
and set a new Exception
object, or do nothing:
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use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
use Symfony\Component\HttpFoundation\Response;
public function onKernelException(GetResponseForExceptionEvent $event)
{
$exception = $event->getException();
$response = new Response();
// setup the Response object based on the caught exception
$event->setResponse($response);
// you can alternatively set a new Exception
// $exception = new \Exception('Some special exception');
// $event->setException($exception);
}
Note
As Symfony ensures that the Response status code is set to the most
appropriate one depending on the exception, setting the status on the
response won't work. If you want to overwrite the status code (which you
should not without a good reason), set the X-Status-Code
header:
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$response = new Response(
'Error',
404, // this status code will be ignored
array(
'X-Status-Code' => 200 // this status code will actually be sent to the client
)
);
See also
Read more on the kernel.exception event.
These are the built-in Symfony listeners registered to this event:
Listener Class Name | Priority |
---|---|
ProfilerListener | 0 |
ExceptionListener | -128 |