PCLZIP_OPT_ADD_COMMENT

This argument gives the ability to add a comment in the PKZIP archive. If a comment already exists, the added comment is append at the end of the existing comment.

    $archive = new PclZip('test.zip');
    $list = $archive->add("data", PCLZIP_OPT_ADD_COMMENT, "Add a comment after the existing one");
    if ($list == 0) {
      echo "ERROR : ".$archive->errorInfo(true);
    } 

See also PCLZIP_OPT_COMMENT and PCLZIP_OPT_PREPEND_COMMENT