How to Create a custom Data Collector

Creating a custom Data Collector

A data collector is a PHP class that implements the DataCollectorInterface. For convenience, your data collectors can also extend from the DataCollector 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\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\DataCollector\DataCollector;

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

    public function reset()
    {
        $this->data = [];
    }

    public function getName()
    {
        return 'app.request_collector';
    }

    // ...
}

collect() method:

Stores the collected data in local properties ($this->data if you extend from DataCollector). If the data to collect cannot be obtained through the request or response, inject the needed services in the data collector.

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. Use it to remove all the information collected with the collect() method.

getName() method:

Returns the collector identifier, which must be unique in the application. This value is used later to access the collector information (see How to Use the Profiler in a Functional Test) so it's recommended to return a string which is short, lowercase and without white spaces.

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).

Enabling Custom Data Collectors

If you're using the default services.yaml configuration with autoconfigure, then Symfony will automatically see your new data collector! Your collect() method should be called the next time you refresh.

If you're not using autoconfigure, you can also manually wire your service and tag it with data_collector.

Adding Web Profiler Templates

The information collected by your data collector can be displayed both in the web debug toolbar and in the web profiler. To do so, you need to create a Twig template that includes some specific blocks.

However, first you must add some getters in the data collector class to give the template access to the collected information:

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

use Symfony\Component\HttpKernel\DataCollector\DataCollector;

class RequestCollector extends DataCollector
{
    // ...

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

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

In the simplest case, you want to display the information in the toolbar without providing a profiler panel. This requires to define the toolbar block and set the value of two variables called icon and text:

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{% 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 %}

If the toolbar panel includes extended web profiler information, the Twig template must also define additional blocks:

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{% 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 %}

The menu and panel blocks are the only required blocks to define the contents displayed in the web profiler panel associated with this data collector. All blocks have access to the collector object.

Finally, to enable the data collector template, override your service configuration to specify a tag that contains the template:

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# config/services.yaml
services:
    App\DataCollector\RequestCollector:
        tags:
            -
                name:     data_collector
                template: 'data_collector/template.html.twig'
                # must match the value returned by the getName() method
                id:       'app.request_collector'
                # optional priority
                # 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">
            <!-- priority="300" -->
            <tag name="data_collector"
                template="data_collector/template.html.twig"
                id="app.request_collector"
            />
        </service>
    </services>
</container>

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

use App\DataCollector\RequestCollector;

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

    $services->set(RequestCollector::class)
        ->autowire()
        ->tag('data_collector', [
            'template' => 'data_collector/template.html.twig',
            'id'       => 'app.request_collector',
            // 'priority' => 300,
        ]);
};

The position of each panel in the toolbar is determined by the collector priority. Priorities are defined as positive or negative integers and they default to 0. Most built-in collectors use 255 as their priority. If you want your collector to be displayed before them, use a higher value (like 300).