[Symfony2] example usage of streamed response and post response code execution

UserController.php

<?php

/*
 * Example usage of streamed response and post response code execution.
 *
 * @author Pierre Minnieur <pierre.minnieur@sensiolabs.de>
 *
 * @see https://github.com/symfony/symfony/pull/2791
 * @see https://github.com/symfony/symfony/pull/2935
 * @see https://github.com/sensio/SensioFrameworkExtraBundle/pull/86
 */

namespace Acme\DemoBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\HttpKernel\Event\PostResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;

use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Method;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template;

use Doctrine\ORM\ORMException;

use Acme\DemoBundle\Entity\User;
use Acme\DemoBundle\Form\Type\UserType;

class UserController extends Controller
{
    /**
     * @Route("/user/register")
     * @Method({"GET", "POST"})
     * @Template(streamable=true)
     */
    public function registerAction()
    {
        $form = $this->createForm(new UserType(), new User());
        if ($this->getRequest()->getMethod() == 'POST') {
            $form->bindRequest($this->getRequest());

            if ($form->isValid()) {
                $user = $form->getData();

                try {
                    $em = $this->getDoctrine()->getEntityManagerForClass('Acme\DemoBundle\Entity\User');
                    $em->persist($user);
                    $em->flush();

                    $this->get('session')->setFlash('success', 'user.register.success');
                } catch (ORMException $e) {
                    $this->get('session')->setFlash('error', 'user.register.failure');
                }

                // post response code execution (mailer)
                $this->get('event_dispatcher')->connect(
                    KernelEvents::TERMINATE,
                    function (PostResponseEvent $event) use ($user) {
                        $mailer = $event->getKernel()->getContainer()->get('mailer');

                        $message = \Swift_Message::newInstance();
                        // ... build your message

                        $mailer->send($message);
                    }
                );

                return $this->redirect($this->generateUrl('_demo'));
            } else {
                $this->get('session')->setFlash('warning', 'user.register.validation');
            }
        }

        return array( // streamed response
            'user' => $form->getData(),
            'form' => $form->createView(),
        );
    }
}