/**
  * @usage Create zip from attached files
  * @param $ID
  * @return mixed|string|\WP_Error
  */
 public static function Zip($ID)
 {
     $files = self::getFiles($ID);
     $zipped = get_post_meta($ID, "__wpdm_zipped_file", true);
     if (count($files) > 0) {
         if ($zipped == '' || !file_exists($zipped)) {
             $zipped = UPLOAD_DIR . sanitize_file_name(get_the_title($ID)) . '-' . $ID . '.zip';
             $zipped = \WPDM\FileSystem::zipFiles($files, $zipped);
             return $zipped;
         }
     }
     return new \WP_Error(404, __('No File Attached!', 'wpdmpro'));
 }
/**
 * @usage Create ZIP from given file list
 * @param $files
 * @param $zipname
 * @return bool|string
 */
function wpdm_zip_files($files, $zipname)
{
    return \WPDM\FileSystem::zipFiles($files, $zipname);
}