I was working on a system that needed generate a PDF report of a view, I solved it as follows:

function report_view() {
	...
	$this->render();
	require_once ('vendors/dompdf/dompdf_config.inc.php'); // import dompdf library
	$dompdf = new DOMPDF();
	$dompdf->load_html($this->output);
	$dompdf->set_paper("a4", "landscape" );
	$dompdf->render();
	$dompdf->stream('ReportExample_'.date('d_M_Y').'.pdf');
	exit(0);
}

You can see, that I used “$this->output” as parameter of load_html to get the output of the view.

I used the dompdf library.