Requests::updateCommentsAmount PHP Method

    public function updateCommentsAmount($requestId, $amount)
    {
        $sth = $this->db->prepare('UPDATE requests SET comments = comments + ? WHERE id = ?');
        $sth->bindParam(1, $amount, PDO::PARAM_INT);
        $sth->bindParam(2, $requestId, PDO::PARAM_INT);
        $sth->execute();
    }