public function addEmptyDir($directoryPath, $options = NULL) {
    if ($this->isFinalized) {
      return false;
    }
    $defaultOptions = array(
    		'timestamp' => NULL,
    		'comment' => NULL,
    );
    if (is_null($options)) {
    	$options = array();
    }
    $options = array_merge($defaultOptions, $options);

    $directoryPath = self::normalizeFilePath($directoryPath) . '/';

    if (strlen($directoryPath) > 0) {
      $gpFlags = 0x0000;
      $gzMethod = COMPR::STORE; // Compression type 0 = stored

      list($gpFlags, $lfhLength) = $this->beginFile($directoryPath, True, $options['comment'], $options['timestamp'], $gpFlags, $gzMethod);
      // build cdRec
      $this->cdRec[] = $this->buildCentralDirectoryHeader($directoryPath, $options['timestamp'], $gpFlags, $gzMethod,
          Count64::construct(0, !$this->zip64), Count64::construct(0, !$this->zip64), 0, $this->extFileAttrDir, True);

      // calc offset
      $this->offset->add($lfhLength);

      return true;
    }
    return false;
  }