<?php $string = file_get_contents("bl-languages/en.json"); $english = json_decode($string, true); $string = file_get_contents("bl-languages/ja_JP.json"); $spanish = json_decode($string, true); $tmp = array(); foreach($english as $key=>$value) { if (isset($spanish[$key])) { $tmp[$key] = $spanish[$key]; } else { $tmp[$key] = $value; } } echo json_encode($tmp, JSON_UNESCAPED_UNICODE);