Online PHP editor | refs for lSKE2

<?php $initial_array = Array ( '061716v' => 1, '061610A' => 1, '062433AP' => 1, '063868M' => 2, '059173V' => 3, '061579A' => 3, '062404AP' => 3, '059179V' => 4, '061582A' => 4, '061697V' => 4, '062407AP' => 4 ); $final_array = []; foreach($initial_array as $key=>$val){ $final_array[$val] = isset($final_array[$val]) ? $final_array[$val].','.$key : $key; } print_r($final_array);