Profiler

Installation

In applications using Symfony Flex, run this command to install the profiler Symfony pack before using it:

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$ composer require --dev symfony/profiler-pack

Now, browse any page of your application in the development environment to let the profiler collect information. Then, click on any element of the debug toolbar injected at the bottom of your pages to open the web interface of the Symfony Profiler, which will look like this:

Accessing Profiling Data Programmatically

Most of the times, the profiler information is accessed and analyzed using its web-based interface. However, you can also retrieve profiling information programmatically thanks to the methods provided by the profiler service.

When the response object is available, use the loadProfileFromResponse() method to access to its associated profile:

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// ... $profiler is the 'profiler' service
$profile = $profiler->loadProfileFromResponse($response);

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. Using this token, you can access the profile of any past response thanks to the loadProfile() method:

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$token = $response->headers->get('X-Debug-Token');
$profile = $profiler->loadProfile($token);

The profiler service also provides the find() method to look for tokens based on some criteria:

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

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

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

// gets the latest 10 tokens for requests that happened between 2 and 4 days ago
$tokens = $profiler->find('', '', 10, '', '4 days ago', '2 days ago');

Data Collectors

The profiler gets its information using some services called "data collectors". Symfony comes with several collectors that get information about the request, the logger, the routing, the cache, etc.

Run this command to get the list of collectors actually enabled in your app:

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$ php bin/console debug:container --tag=data_collector

You can also create your own data collector to store any data generated by your app and display it in the debug toolbar and the profiler web interface.

Timing the Execution of the Application

If you want to measure the time some tasks take in your application, there's no need to create a custom data collector. Instead, use the built-in utilities to profile Symfony applications.

Enabling the Profiler Conditionally

Symfony Profiler cannot be enabled/disabled conditionally using matchers, because that feature was removed in Symfony 4.0. However, you can use the enable() and disable() methods of the Profiler class in your controllers to manage the profiler programmatically:

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use Symfony\Component\HttpKernel\Profiler\Profiler;
// ...

class DefaultController
{
    // ...

    public function someMethod(?Profiler $profiler)
    {
        // $profiler won't be set if your environment doesn't have the profiler (like prod, by default)
        if (null !== $profiler) {
            // if it exists, disable the profiler for this particular controller action
            $profiler->disable();
        }

        // ...
    }
}

In order for the profiler to be injected into your controller you need to create an alias pointing to the existing profiler service:

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# config/services_dev.yaml
services:
    Symfony\Component\HttpKernel\Profiler\Profiler: '@profiler'

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<!-- config/services_dev.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        https://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <service id="Symfony\Component\HttpKernel\Profiler\Profiler" alias="profiler"/>
    </services>
</container>

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// config/services_dev.php
use Symfony\Component\HttpKernel\Profiler\Profiler;

$container->setAlias(Profiler::class, 'profiler');

Updating the Web Debug Toolbar After AJAX Requests

Single-page applications (SPA) are web applications that interact with the user by dynamically rewriting the current page rather than loading entire new pages from a server.

By default, the debug toolbar displays the information of the initial page load and doesn't refresh after each AJAX request. However, you can set the Symfony-Debug-Toolbar-Replace header to a value of 1 in the response to the AJAX request to force the refresh of the toolbar:

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$response->headers->set('Symfony-Debug-Toolbar-Replace', 1);

Ideally this header should only be set during development and not for production. To do that, create an event subscriber and listen to the kernel.response event:

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use Symfony\Component\HttpKernel\Event\ResponseEvent;

// ...

public function onKernelResponse(ResponseEvent $event)
{
    if (!$event->getKernel()->isDebug()) {
        return;
    }

    $request = $event->getRequest();
    if (!$request->isXmlHttpRequest()) {
        return;
    }

    $response = $event->getResponse();
    $response->headers->set('Symfony-Debug-Toolbar-Replace', 1);
}