Online PHP editor | refs for uFbFK

<?php $arr = [ "one" => "one", "two" => "two", "group1" => [ "three" => "three", "four" => "four", "group2" => [ "five" => "five", ], ], "group3" => [ "six" => "six", ] ]; function mergeRecursive(array $array, $result = []) { foreach($array as $k => $v) { if(!is_array($array)) $result[] = $v; else $result[] = $k . mergeRecursive($v); } return $result; } $result = mergeRecursive($arr); print_r($result);