symfony/src/Symfony/Bundle/FrameworkBundle/Resources/config/router.php

<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

/*
 * This file implements rewrite rules for PHP built-in web server.
 *
 * See: http://www.php.net/manual/en/features.commandline.webserver.php
 *
 * If you have custom directory layout, then you have to write your own router
 * and pass it as a value to 'router' option of server:run command.
 *
 * @author: Michał Pipa <michal.pipa.xsolve@gmail.com>
 */

if (isset($_SERVER['SCRIPT_FILENAME'])) {
    return false;
}

$_SERVER['SCRIPT_FILENAME'] = $_SERVER['DOCUMENT_ROOT'].DIRECTORY_SEPARATOR.'app_dev.php';

require 'app_dev.php';