Online PHP editor | refs for 7G2kW

<?php $array = Array ( '0' => (object)[ 'id' => 17, 'res_id' => 10, 'cat_id' => 3 ], '1' => (object)[ 'id' => 18, 'res_id' => 10, 'cat_id' => 4 ], '2' => (object)[ 'id' => 52, 'res_id' => 19, 'cat_id' => 1 ], '3' => (object)[ 'id' => 53, 'res_id' => 19, 'cat_id' => 3 ], '4' => (object)[ 'id' => 54, 'res_id' => 19, 'cat_id' => 4 ] ); $result = array_map(function($x){ return $x->cat_id; }, $array); print_r($result);