class correct {
        public function correctaao($arg) {
                $string = preg_replace('/å/', 'a', $arg);
                $string2 = preg_replace('/ä/', 'a', $string);
                $string3 = preg_replace('/ö/', 'o', $string2);
                return $string3;

        }
}
$corr = new correct();
echo $corr->correctaao("hej ååäö");