private function download($productLineName) {
        $productLineName = str_replace("\"", "", $productLineName);
        if (headers_sent())
            throw new DownloadZipExporterException("could download zip archive");
        header("Content-Type: application/zip");
        header("Content-Disposition: attachment; filename=\"$productLineName.zip\"");
        set_time_limit(0);
        $file = @fopen($this->target, "rb");
        while(!feof($file)) {
            print(@fread($file, 1024*8));
            ob_flush();
            flush();
        }
    }