code: public function exportAction()
      {
          $em = $this->getDoctrine()->getManager();
          $chillSecurityHelper = $this->get('chill.main.security.authorization.helper');
          $user = $this->get('security.context')->getToken()->getUser();
  
          $reachableCenters = $chillSecurityHelper->getReachableCenters($user,
              new Role('CHILL_PERSON_SEE'));
  
          $personRepository = $em->getRepository('ChillPersonBundle:Person');
          $qb = $personRepository->createQueryBuilder('p');
          $qb->where($qb->expr()->in('p.center', ':centers'))
              ->setParameter('centers', $reachableCenters);
          $persons = $qb->getQuery()->getResult();
  
          $response = $this->render('ChillPersonBundle:Person:export.csv.twig',
              array(
                  'persons' => $persons,
                  'cf_group' => $this->getCFGroup()));
          $response->headers->set('Content-Type', 'text/csv; charset=utf-8');
          $response->headers->set('Content-Disposition', 'attachment; filename="export_person.csv"');
  
          return $response;
      }
docs: Return a csv file with all the persons
  
  @return A csv file with all the persons