AjaxController.php

in file: AjaxController.php
<?php

/*
Performance wise, if you just need to return a simple text to the user
and you want to save resources, you may want to avoid loading the templating
system and return the text directly the the user

*/

namespace Bundle\RabbitBundle\Controller;

use Symfony\Framework\WebBundle\Controller;

class AjaxController extends Controller
{
  public function renderText($content)
  {
    $response = $this->container->getResponseService();
    $response->setContent($content);

    return $response;
  }
}

//in file DashboardController.php
<?php

namespace Bundle\RabbitBundle\Controller;

use Bundle\RabbitBundle\Controller\AjaxController;
use Bundle\RabbitBundle\Model\Queue;

class DashboardController extends AjaxController
{
  public function indexAction()
  {
    return $this->renderText(
        json_encode(array(
            'dashboard' => array(Queue::findForVhosts())
          ))
      );
  }
}