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 Programmatically

Symfony Profiler can be enabled and disabled programmatically. 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\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\Event\ResponseEvent;
use Symfony\Component\HttpKernel\KernelInterface;

// ...

class MySubscriber implements EventSubscriberInterface
{
    public function __construct(
        private KernelInterface $kernel,
    ) {
    }

    // ...

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

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

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

Creating a Data Collector

The Symfony Profiler obtains its profiling and debug information using some special classes called data collectors. Symfony comes bundled with a few of them, but you can also create your own.

A data collector is a PHP class that implements the DataCollectorInterface. For convenience, your data collectors can also extend from the AbstractDataCollector class, which implements the interface and provides some utilities and the $this->data property to store the collected information.

The following example shows a custom collector that stores information about the request:

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// src/DataCollector/RequestCollector.php
namespace App\DataCollector;

use Symfony\Bundle\FrameworkBundle\DataCollector\AbstractDataCollector;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

class RequestCollector extends AbstractDataCollector
{
    public function collect(Request $request, Response $response, \Throwable $exception = null)
    {
        $this->data = [
            'method' => $request->getMethod(),
            'acceptable_content_types' => $request->getAcceptableContentTypes(),
        ];
    }
}

These are the method that you can define in the data collector class:

collect() method:

Stores the collected data in local properties ($this->data if you extend from AbstractDataCollector). If you need some services to collect the data, inject those services in the data collector constructor.

Caution

The collect() method is only called once. It is not used to "gather" data but is there to "pick up" the data that has been stored by your service.

Caution

As the profiler serializes data collector instances, you should not store objects that cannot be serialized (like PDO objects) or you need to provide your own serialize() method.

reset() method:

It's called between requests to reset the state of the profiler. By default it only empties the $this->data contents, but you can override this method to do additional cleaning.

getName() method:

Returns the collector identifier, which must be unique in the application. By default it returns the FQCN of the data collector class, but you can override this method to return a custom name (e.g. app.request_collector). This value is used later to access the collector information (see How to Use the Profiler in a Functional Test) so you may prefer using short strings instead of FQCN strings.

The collect() method is called during the kernel.response event. If you need to collect data that is only available later, implement LateDataCollectorInterface and define the lateCollect() method, which is invoked right before the profiler data serialization (during kernel.terminate event).

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// src/DataCollector/RequestCollector.php
namespace App\DataCollector;

use Symfony\Bundle\FrameworkBundle\DataCollector\AbstractDataCollector;

class RequestCollector extends AbstractDataCollector
{
    // ...

    public static function getTemplate(): ?string
    {
        return 'data_collector/template.html.twig';
    }

    public function getMethod()
    {
        return $this->data['method'];
    }

    public function getAcceptableContentTypes()
    {
        return $this->data['acceptable_content_types'];
    }
}

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{# templates/data_collector/template.html.twig #}
{% extends '@WebProfiler/Profiler/layout.html.twig' %}

{% block toolbar %}
    {% set icon %}
        {# this is the content displayed as a panel in the toolbar #}
        <svg xmlns="http://www.w3.org/2000/svg"> ... </svg>
        <span class="sf-toolbar-value">Request</span>
    {% endset %}

    {% set text %}
        {# this is the content displayed when hovering the mouse over
           the toolbar panel #}
        <div class="sf-toolbar-info-piece">
            <b>Method</b>
            <span>{{ collector.method }}</span>
        </div>

        <div class="sf-toolbar-info-piece">
            <b>Accepted content type</b>
            <span>{{ collector.acceptableContentTypes|join(', ') }}</span>
        </div>
    {% endset %}

    {# the 'link' value set to 'false' means that this panel doesn't
       show a section in the web profiler #}
    {{ include('@WebProfiler/Profiler/toolbar_item.html.twig', { link: false }) }}
{% endblock %}

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{% set icon %}
    {{ include('data_collector/icon.svg') }}
    {# ... #}
{% endset %}

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{# templates/data_collector/template.html.twig #}
{% extends '@WebProfiler/Profiler/layout.html.twig' %}

{% block toolbar %}
    {% set icon %}
        {# ... #}
    {% endset %}

    {% set text %}
        <div class="sf-toolbar-info-piece">
            {# ... #}
        </div>
    {% endset %}

    {{ include('@WebProfiler/Profiler/toolbar_item.html.twig', { 'link': true }) }}
{% endblock %}

{% block head %}
    {# Optional. Here you can link to or define your own CSS and JS contents. #}
    {# Use {{ parent() }} to extend the default styles instead of overriding them. #}
{% endblock %}

{% block menu %}
    {# This left-hand menu appears when using the full-screen profiler. #}
    <span class="label">
        <span class="icon"><img src="..." alt=""/></span>
        <strong>Request</strong>
    </span>
{% endblock %}

{% block panel %}
    {# Optional, for showing the most details. #}
    <h2>Acceptable Content Types</h2>
    <table>
        <tr>
            <th>Content Type</th>
        </tr>

        {% for type in collector.acceptableContentTypes %}
        <tr>
            <td>{{ type }}</td>
        </tr>
        {% endfor %}
    </table>
{% endblock %}

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# config/services.yaml
services:
    App\DataCollector\RequestCollector:
        tags:
            -
                name: data_collector
                # must match the value returned by the getName() method
                id: 'App\DataCollector\RequestCollector'
                # optional template (it has more priority than the value returned by getTemplate())
                template: 'data_collector/template.html.twig'
                # optional priority (positive or negative integer; default = 0)
                # priority: 300

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<!-- config/services.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="App\DataCollector\RequestCollector">
            <!-- the 'template' attribute has more priority than the value returned by getTemplate() -->
            <tag name="data_collector"
                id="App\DataCollector\RequestCollector"
                template="data_collector/template.html.twig"
            />
            <!-- optional 'priority' attribute (positive or negative integer; default = 0) -->
            <!-- priority="300" -->
        </service>
    </services>
</container>

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// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;

use App\DataCollector\RequestCollector;

return function(ContainerConfigurator $containerConfigurator) {
    $services = $containerConfigurator->services();

    $services->set(RequestCollector::class)
        ->tag('data_collector', [
            'id' => RequestCollector::class,
            // optional template (it has more priority than the value returned by getTemplate())
            'template' => 'data_collector/template.html.twig',
            // optional priority (positive or negative integer; default = 0)
            // 'priority' => 300,
        ]);
};