How can i get the single result using DQL in symfony2

                $allProfiles = $em->createQuery($dql)
                                ->setParameter('user_id',$user_id)
                                ->setMaxResults(1)
                                ->getResult();
                return $allProfiles[0];

The right method is:

$singleProfile = $em->createQuery($dql)
                    ->setParameter('user_id',$user_id)
                    ->getSingleResult();

To prevent error then no results try this:

$singleProfile = $em->createQuery($dql)
                    ->setParameter('user_id',$user_id)
                    ->getOneOrNullResult();