array_push() merging multiple array

That's because you're adding a non-object to the last element of the array.

Here i suppose you get an array of objects with the name property

$competition_all = Competition::all();

Here you add a key=>value pair to the last element of the objects array

$newCompete = array('name'=>'Others');
array_push($competition_all, $newCompete);

Here you walk through the array of objects and when it comes to the last element the "$competition_games->name" has no name property

foreach ($competition_all as $competition_games) {
            $this->competition_games[$competition_games->name] = $competition_games->name;
        }

Try something like including a stdclass for it like :

$newCompete = new StdClass();
$newCompete->name = 'Others';
array_push($competition_all, $newCompete);