getRequestType()¶

The getRequestType() method allows listeners to know the type of the request. For instance, if a listener must only be active for master requests, add the following code at the beginning of your listener method:

use Symfony\Component\HttpKernel\HttpKernelInterface;

if (HttpKernelInterface::MASTER_REQUEST !== $event->getRequestType()) {
    // return immediately
    return;
}

kernel.request Event¶

Event Class: GetResponseEvent

The goal of this event is to either return a Response object immediately or setup variables so that a Controller can be called after the event. Any listener can return a Response object via the setResponse() method on the event. In this case, all other listeners won't be called.

This event is used by FrameworkBundle to populate the _controller Request attribute, via the RouterListener. RequestListener uses a RouterInterface object to match the Request and determine the Controller name (stored in the _controller Request attribute).

kernel.controller Event¶

Event Class: FilterControllerEvent

This event is not used by FrameworkBundle, but can be an entry point used to modify the controller that should be executed:

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);
}

kernel.view Event¶

Event Class: GetResponseForControllerResultEvent

This event is not used by 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:

use Symfony\Component\HttpKernel\Event\GetResponseForControllerResultEvent;
use Symfony\Component\HttpFoundation\Response;

public function onKernelView(GetResponseForControllerResultEvent $event)
{
    $val = $event->getControllerResult();
    $response = new Response();
    // some how customize the Response from the return value

    $event->setResponse($response);
}

kernel.response Event¶

Event Class: FilterResponseEvent

The purpose of this event is to allow other systems to modify or replace the Response object after its creation:

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.

kernel.exception Event¶

Event Class: GetResponseForExceptionEvent

FrameworkBundle registers an ExceptionListener that forwards the Request to a given Controller (the value of the exception_listener.controller parameter -- must be in the class::method notation).

A listener on this event can create and set a Response object, create and set a new Exception object, or do nothing:

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);
}

Using the Web Debug Toolbar¶

In the development environment, the web debug toolbar is available at the bottom of all pages. It displays a good summary of the profiling data that gives you instant access to a lot of useful information when something does not work as expected.

If the summary provided by the Web Debug Toolbar is not enough, click on the token link (a string made of 13 random characters) to access the Web Profiler.

Analyzing Profiling data with the Web Profiler¶

The Web Profiler is a visualization tool for profiling data that you can use in development to debug your code and enhance performance; but it can also be used to explore problems that occur in production. It exposes all information collected by the profiler in a web interface.

Accessing the Profiling information¶

You don't need to use the default visualizer to access the profiling information. But how can you retrieve profiling information for a specific request after the fact? When the profiler stores data about a Request, it also associates a token with it; this token is available in the X-Debug-Token HTTP header of the Response:

$profile = $container->get('profiler')->loadProfileFromResponse($response);

$profile = $container->get('profiler')->loadProfile($token);

Use the find() method to access tokens based on some criteria:

// get the latest 10 tokens
$tokens = $container->get('profiler')->find('', '', 10);

// get the latest 10 tokens for all URL containing /admin/
$tokens = $container->get('profiler')->find('', '/admin/', 10);

// get the latest 10 tokens for local requests
$tokens = $container->get('profiler')->find('127.0.0.1', '', 10);

If you want to manipulate profiling data on a different machine than the one where the information were generated, use the export() and import() methods:

// on the production machine
$profile = $container->get('profiler')->loadProfile($token);
$data = $profiler->export($profile);

// on the development machine
$profiler->import($data);

Configuration¶

The default Symfony2 configuration comes with sensible settings for the profiler, the web debug toolbar, and the web profiler. Here is for instance the configuration for the development environment:

When only-exceptions is set to true, the profiler only collects data when an exception is thrown by the application.

When intercept-redirects is set to true, the web profiler intercepts the redirects and gives you the opportunity to look at the collected data before following the redirect.

When verbose is set to true, the Web Debug Toolbar displays a lot of information. Setting verbose to false hides some secondary information to make the toolbar shorter.

If you enable the web profiler, you also need to mount the profiler routes:

As the profiler adds some overhead, you might want to enable it only under certain circumstances in the production environment. The only-exceptions settings limits profiling to 500 pages, but what if you want to get information when the client IP comes from a specific address, or for a limited portion of the website? You can use a request matcher: