$char) { if ($char == $solution[$pos]) { $out[$pos] = "$char"; unset($toCheck[$pos], $solution[$pos]); } } foreach ($toCheck as $pos => $char) { if (false !== $solPos = array_search($char, $solution)) { $out[$pos] = "$char"; unset($toCheck[$pos], $solution[$solPos]); } } $out += $toCheck; ksort($out); return implode($out); } var_dump(checkWord('abaac', 'aabbc'));