The configuration format

Symfony2 can handle configuration in different formats: YAML, XML, and annotations. The main configuration files within app/config are provided with the YAML format. XML is usually harder to read, and is used only with third-party bundles.

While both YAML and XML configuration are pretty straightforward and need no explanations, we should stop by annotations for a while. As an example, see the AppBundle/Controller/DefaultController class:

namespace AppBundle\Controller;

use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;

class DefaultController extends Controller
{
    /**
     * @Route("/", name="homepage")
     */
    public function indexAction(Request $request)
    {
        // replace this example code with whatever you need
        return $this->render('default/index.html.twig', array(
            'base_dir' => realpath(
                $this->container
                     ->getParameter...