Symfony2框架下一个简单Ajax留言板

<?php

namespace Dp\DriveplusBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\HttpFoundation\Response;
use Dp\DriveplusBundle\Entity\Messageboard;

class MessageController extends Controller
{    
    public function indexAction()
    {
        $em = $this->getDoctrine()->getEntityManager();
        $query = $em->createQuery(
             'SELECT m FROM DpDriveplusBundle:Messageboard m ORDER BY m.id DESC'
         );
        $comments = $query->getResult();
        $count = count($comments);
        return $this->render('DpDriveplusBundle:Message:index.html.twig', array('comments'=>$comments, 'count'=>$count));
    }
    
    public function ajaxAction()
    {      
        $request = $this->getRequest();
        $ret = '';
             
        if ('POST' === $request->getMethod()) {       
            $name = $request->get('name');
            $message = $request->get('message');          
            $ret = '姓名：'.$name.'<br/> 留言内容：'.$message.'<hr/>';
            
            $comment = new Messageboard();
            $comment->setName($name);
            $comment->setMessage($message);
            $em = $this->getDoctrine()->getEntityManager();
            $em->persist($comment);       
            $em->flush();
            
            return new Response($ret);
        }
    }
}