SignupHandler.php

<?php

namespace JStout\MainBundle\Form\User;

use Symfony\Component\Form\Form;

class SignupHandler
{
    protected $form;

    public function __construct(Form $form)
    {
        $this->form = $form;
    }

    public function process()
    {
        // Form validation successful!... :)
        if ($this->form->isValid()) {
            ... do all the uber cool user signup stuff ...
        }

        // Form validation failed... :(
        return false;
    }
}

UserController.php

<?php

namespace JStout\MainBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller,
    Sensio\Bundle\FrameworkExtraBundle\Configuration\Route,
    Sensio\Bundle\FrameworkExtraBundle\Configuration\Template,
    JStout\MainBundle\Entity\User,
    JStout\MainBundle\Form\User\SignupType,
    JStout\MainBundle\Form\User\SignupHandler;

/**
 * @Route("/user")
 */
class UserController extends Controller
{
    /**
     * @Route(name="user")
     * @Template()
     */
    public function indexAction()
    {
        return array();
    }

    /**
     * @Route("/sign-up", name="user_signup")
     * @Template()
     */
    public function signupAction()
    {
        $user = new User();
        $form = $this->get('form.factory')->create(new SignupType(), $user);

        $request = $this->get('request');

        if ($request->getMethod() == 'POST') {
            $form->bindRequest($request);
            
            $formHandler = new SignupHandler($form);

            if ($formHandler->process()) {
                return $this->redirect($this->generateUrl('success');
            }
        }

        return array(
            'form' => $form->createView()
        );
    }
}