if($count > 0)
            $sql= "UPDATE dynamic_password SET password = :password WHERE userid = :userid LIMIT 1";
        else
            $sql = "INSERT INTO dynamic_password (userid, password) VALUES (:userid, :password)";

        $q = $db->prepare($sql);
        $q->execute(array(
            ':userid' => $userid,
            ':password' => $dynamic_password)
        );