app.php

<?php

use Symfony\Component\HttpFoundation\Request;

umask(0000);

if (!isset($_SERVER['APPLICATION_ENV'])) {
    $_SERVER['APPLICATION_ENV'] = 'prod';
}

/**
 * @var Composer\Autoload\ClassLoader
 */
$loader = require __DIR__.'/../app/autoload.php';
include_once __DIR__.'/../var/bootstrap.php.cache';


if ($_SERVER['APPLICATION_ENV'] == 'prod' && isset($_SERVER['AUTOLOAD_APC']) && $_SERVER['AUTOLOAD_APC']) {
// Enable APC for autoloading to improve performance.
// You should change the ApcClassLoader first argument to a unique prefix
// in order to prevent cache key conflicts with other applications
// also using APC.
    $apcLoader = new Symfony\Component\ClassLoader\ApcClassLoader(sha1(__FILE__), $loader);
    $loader->unregister();
    $apcLoader->register(true);
}

$kernel = new AppKernel($_SERVER['APPLICATION_ENV'], $_SERVER['APPLICATION_ENV'] == 'dev');
$kernel->loadClassCache();

$request = Request::createFromGlobals();
$response = $kernel->handle($request);
$response->send();
$kernel->terminate($request, $response);

Utilisation Apache :
SetEnv APPLICATION_ENV "dev"