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How to Restrict Route Matching through Conditions

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How to Restrict Route Matching through Conditions¶

As you've seen, a route can be made to match only certain routing wildcards (via regular expressions), HTTP methods, or host names. But the routing system can be extended to have an almost infinite flexibility using conditions:

YAML

contact:
    path:     /contact
    defaults: { _controller: AcmeDemoBundle:Main:contact }
    condition: "context.getMethod() in ['GET', 'HEAD'] and request.headers.get('User-Agent') matches '/firefox/i'"

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">AcmeDemoBundle:Main:contact</default>
        <condition>context.getMethod() in ['GET', 'HEAD'] and request.headers.get('User-Agent') matches '/firefox/i'</condition>
    </route>
</routes>

PHP

use Symfony\Component\Routing\RouteCollection;
use Symfony\Component\Routing\Route;

$collection = new RouteCollection();
$collection->add('contact', new Route(
    '/contact', array(
        '_controller' => 'AcmeDemoBundle:Main:contact',
    ),
    array(),
    array(),
    '',
    array(),
    array(),
    'context.getMethod() in ["GET", "HEAD"] and request.headers.get("User-Agent") matches "/firefox/i"'
));

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.