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How to Restrict Route Matching through Conditions

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How to Restrict Route Matching through Conditions¶

A route can be made to match only certain routing placeholders (via regular expressions), HTTP methods, or host names. If you need more flexibility to define arbitrary matching logic, use the conditions routing option:

Annotations

// src/Controller/DefaultController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\Routing\Annotation\Route;

class DefaultController extends AbstractController
{
    /**
     * @Route(
     *     "/contact",
     *     name="contact",
     *     condition="context.getMethod() in ['GET', 'HEAD'] and request.headers.get('User-Agent') matches '/firefox/i'"
     * )
     *
     * expressions can also include config parameters
     * condition: "request.headers.get('User-Agent') matches '%app.allowed_browsers%'"
     */
    public function contact()
    {
        // ...
    }
}

YAML

# config/routes.yaml
contact:
    path:       /contact
    controller: 'App\Controller\DefaultController::contact'
    condition:  "context.getMethod() in ['GET', 'HEAD'] and request.headers.get('User-Agent') matches '/firefox/i'"
    # expressions can also include config parameters
    # condition: "request.headers.get('User-Agent') matches '%app.allowed_browsers%'"

XML

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

    <route id="contact" path="/contact">
        <default key="_controller">App\Controller\DefaultController::contact</default>
        <condition>context.getMethod() in ['GET', 'HEAD'] and request.headers.get('User-Agent') matches '/firefox/i'</condition>
        <!-- expressions can also include config parameters -->
        <!-- <condition>request.headers.get('User-Agent') matches '%app.allowed_browsers%'</condition> -->
    </route>
</routes>

PHP

// config/routes.php
use Symfony\Component\Routing\RouteCollection;
use Symfony\Component\Routing\Route;

$routes = new RouteCollection();
$routes->add('contact', new Route(
    '/contact', array(
        '_controller' => 'App\Controller\DefaultController::contact',
    ),
    array(),
    array(),
    '',
    array(),
    array(),
    'context.getMethod() in ["GET", "HEAD"] and request.headers.get("User-Agent") matches "/firefox/i"'
    // expressions can also include config parameters
    // 'request.headers.get("User-Agent") matches "%app.allowed_browsers%"'
));

return $collection;

The condition is an expression, and you can learn more about its syntax here: The Expression Syntax. With this, the route won't match unless the HTTP method is either GET or HEAD and if the User-Agent header matches firefox.

You can do any complex logic you need in the expression by leveraging two variables that are passed into the expression:

context: An instance of RequestContext, which holds the most fundamental information about the route being matched.
request: The Symfony Request object (see Request).

Caution

Conditions are not taken into account when generating a URL.

Behind the scenes, expressions are compiled down to raw PHP. Our example would generate the following PHP in the cache directory:

if (rtrim($pathInfo, '/contact') === '' && (
    in_array($context->getMethod(), array(0 => "GET", 1 => "HEAD"))
    && preg_match("/firefox/i", $request->headers->get("User-Agent"))
)) {
    // ...
}

Because of this, using the condition key causes no extra overhead beyond the time it takes for the underlying PHP to execute.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.