private static function downloadPDF($content, $filename)
{
if (!is_executable(WKPDF_PATH)) {
throw new \Exception('WKPDF is not installed or executable', 666);
}
$pdf = new \WKPDF(WKPDF_PATH);
if (USE_XVFB) {
$pdf->setXVFB(XVFB_PATH);
}
$pdf->set_html($content);
$pdf->render();
$pdf->output(\WKPDF::$PDF_DOWNLOAD, '/tmp/' . $filename);
exit;
}
