php - sorting an array of objects by datetime variable -

i want sort array of object datetime variable, dates situated in future , want date thats closest current date first one.

i'm using following controlleraction in symfony2:

public function fixturesaction(){         if (false === $this->get('security.context')->isgranted('is_authenticated_fully')) {             throw $this->createaccessdeniedexception('unable access page!');         }          $user = $this->get('security.context')->gettoken()->getuser();         $team = $this->getdoctrine()                 ->getrepository('loginloginbundle:team')                 ->findbyuseruserid($user->getuserid());         $matchgameshome = $this->getdoctrine()                         ->getrepository('loginloginbundle:matchgame')                         ->findbyhometeam($team[0]->getname());         $matchgamesaway = $this->getdoctrine()                         ->getrepository('loginloginbundle:matchgame')                         ->findbyawayteam($team[0]->getname());          $matchgames = array_merge($matchgameshome, $matchgamesaway);          $sorted = usort($matchgames, function($a, $b) {             return $a->date->format('u') - $b->date->format('u');         });          return $this->render('loginloginbundle:default:fixtures.html.twig', array("matcharray"=>$sorted));     } 

where sorting:

$sorted = usort($matchgames, function($a, $b) {                 return $a->date->format('u') - $b->date->format('u');             }); 

this yields me following error:

error: cannot access private property login\loginbundle\entity\matchgame::$date in c:\wamp\www\socpronetbeans\src\login\loginbundle\controller\defaultcontroller.php line 675  

line 675 following:

return $a->date->format('u') - $b->date->format('u'); 

what proper way sort array?

since don't know line error speaks of, small shot in dark:

replace

return $a['date']->format('u') - $b['date']->format('u'); 

with

return $a->date->format('u') - $b->date->format('u');