php check credit card expiration

$expires = DateTime::createFromFormat('my', $_POST['expMonth'].$_POST['expYear']);
$now     = new DateTime();

if ($expires < $now) {
    echo 'Expired!';
}

$expires =  date_format( \DateTime::createFromFormat('ym', $cc_expiration),"ym");

$now =  date_format(new \DateTime(),"ym");

if ($expires < $now) {
    return 'Expired!';
}