public function getCards($addressbookId)
    {
        $stmt = $this->pdo->prepare('SELECT id, uri, lastmodified, etag, size FROM '.$this->cardsTableName.' WHERE addressbookid = ?');
        $stmt->execute([$addressbookId]);

        $result = [];
        while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
            $row['etag'] = '"'.$row['etag'].'"';
            $row['lastmodified'] = (int) $row['lastmodified'];
            $result[] = $row;
        }

        return $result;
    }