public function addDirectory($directoryPath, $timestamp = 0, $fileComment = NULL, $extFileAttr = self::EXT_FILE_ATTR_DIR) {
        if ($this->isFinalized) {
            return FALSE;
        }
        $directoryPath = str_replace("\\", "/", $directoryPath);
        $directoryPath = rtrim($directoryPath, "/");

        if (strlen($directoryPath) > 0) {
            $this->buildZipEntry($directoryPath.'/', $fileComment, "\x00\x00", "\x00\x00", $timestamp, "\x00\x00\x00\x00", 0, 0, $extFileAttr);
            return TRUE;
        }
        return FALSE;
    }