Online PHP editor | refs for u2JPj

<?php $arr = array(); $a = [0,1,2,3,4,5]; $b = [0,1,2,3,4,5]; $c = [0,1,2,3,4,5]; $d = [0,1,2,3,4,5]; $e = [0,1,2,3,4,5]; $f = [0,1,2,3,4,5]; $g = [0,1,2,3,4,5]; $arr[] = $a; $arr[] = $b; $arr[] = $c; $arr[0][2] = $d; $arr[0][2][3] = $e; $arr[2][1] = $f; $arr[1] = $g; print_r($arr); function array_keys_recur($myArray, $MAXDEPTH = INF, $depth = 0, $arrayKeys = array()){ if($depth < $MAXDEPTH){ $depth++; $keys = array_keys($myArray); foreach($keys as $key){ if(is_array($myArray[$key])){ $arrayKeys[$key] = array_keys_recursive($myArray[$key], $MAXDEPTH, $depth); } } } return $arrayKeys; } $keys = array_keys_recur($arr); print_r($keys);