example LoginController

LoginController.php

<?php

namespace Xxx\UserBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\Security\Core\SecurityContext;
use Symfony\Component\HttpFoundation\Request;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template;

class LoginController extends Controller
{
    /**
     * @Template()
     *
     * @param Request $request
     * @return array
     */
    public function loginAction(Request $request)
    {
        $session = $request->getSession();

        // get the login error if there is one
        if ($request->attributes->has(SecurityContext::AUTHENTICATION_ERROR)) {
            $error = $request->attributes->get(
                SecurityContext::AUTHENTICATION_ERROR
            );
        } else {
            $error = $session->get(SecurityContext::AUTHENTICATION_ERROR);
            $session->remove(SecurityContext::AUTHENTICATION_ERROR);
        }

        return [
            'last_username' => $session->get(SecurityContext::LAST_USERNAME),
            'error' => $error,
        ];
    }
}