PCLZIP_OPT_NO_COMPRESSION

This argument gives you the ability to add a file in an archive without compressing the file.

    $archive = new PclZip('test.zip');
    $list = $archive->add("data/file.txt", PCLZIP_OPT_NO_COMPRESSION);
    if ($list == 0) {
      echo "ERROR : ".$archive->errorInfo(true);
    }