function upload_files()
    {
        check_ajax_referer( 'wpvivid_ajax', 'nonce' );
        $check=current_user_can('manage_options');
        $check=apply_filters('wpvivid_ajax_check_security',$check);
        if(!$check)
        {
            die();
        }

        try
        {
            $chunk = isset($_REQUEST["chunk"]) ? intval(sanitize_key($_REQUEST["chunk"])) : 0;
            $chunks = isset($_REQUEST["chunks"]) ? intval(sanitize_key($_REQUEST["chunks"])) : 0;

            $fileName = isset($_REQUEST["name"]) ? sanitize_text_field($_REQUEST["name"]) : $_FILES["file"]["name"];

            $backupdir=WPvivid_Setting::get_backupdir();
            $filePath = WP_CONTENT_DIR.DIRECTORY_SEPARATOR.$backupdir.DIRECTORY_SEPARATOR.$fileName;

            $out = @fopen("{$filePath}.part", $chunk == 0 ? "wb" : "ab");

            if ($out)
            {
                // Read binary input stream and append it to temp file
                $options['test_form'] =true;
                $options['action'] ='wpvivid_upload_files';
                $options['test_type'] = false;
                $options['ext'] = 'zip';
                $options['type'] = 'application/zip';

                add_filter('upload_dir', array($this, 'upload_dir'));

                $status = wp_handle_upload($_FILES['async-upload'],$options);

                remove_filter('upload_dir', array($this, 'upload_dir'));

                $in = @fopen($status['file'], "rb");

                if ($in)
                {
                    while ($buff = fread($in, 4096))
                        fwrite($out, $buff);
                }
                else
                {
                    echo wp_json_encode(array('result'=>'failed','error'=>"Failed to open tmp file.path:".$status['file']));
                    die();
                }

                @fclose($in);
                @fclose($out);

                @wp_delete_file($status['file']);
            }
            else
            {
                echo wp_json_encode(array('result'=>'failed','error'=>"Failed to open input stream.path:{$filePath}.part"));
                die();
            }

            if (!$chunks || $chunk == $chunks - 1)
            {
                // Strip the temp .part suffix off
                rename("{$filePath}.part", $filePath);
            }

            echo wp_json_encode(array('result' => WPVIVID_SUCCESS));
        }
        catch (Exception $error)
        {
            $message = 'An exception has occurred. class: '.get_class($error).';msg: '.$error->getMessage().';code: '.$error->getCode().';line: '.$error->getLine().';in_file: '.$error->getFile().';';
            error_log($message);
            echo wp_json_encode(array('result'=>'failed','error'=>$message));
        }
        die();
    }