如何强制在opencart中下载pdf

Question

我已经实现了以pdf格式导出报告的功能。

以下是代码：

            $dompdf_config = new DOMPDF();
            $template = new Template();
            $template->data['products']=$results;
            $html = $template->fetch('report/business_pdf.tpl');
            $dompdf_config->load_html($html);
            $dompdf_config->set_paper('letter', 'portrait');
            $dompdf_config->render();  

            if (file_put_contents('report.pdf', $dompdf_config->output()) !== false) {                    
                $this->redirect('report.pdf');
            }  

但它会在浏览器中打开，那么如何强制下载呢？

更新

之后我添加了代码：

$file = "report.pdf"
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename='.basename($file));
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Length: ' . filesize($file));
ob_clean();
flush();
readfile($file);

获取下载对话框：

对话框中没有打开选项，请帮帮我