LocaleListener.php

<?php
namespace Formation\CoreBundle\Listener;


use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\Event\GetResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;

class LocaleListener implements EventSubscriberInterface
{

    public function onKernelRequest(GetResponseEvent $event)
    {
        $request = $event->getRequest();

        if(!$request->getSession()->has('locale')) {
            $request->getSession()->set('locale', $request->getPreferredLanguage());
        }

        $request->setLocale($request->getSession()->get('locale'));
    }

    public static function getSubscribedEvents()
    {
        return array(KernelEvents::REQUEST => array(array('onKernelRequest', 17)));
    }
}