This error can be caused by many things, but the most notable is when attempting to reuse DomPdf to render more than one PDF.

This is to do with the way the service manager passes a single instance, and DOMPDF does not clean up after itself properly.

Attempting code like:

$html   = $this->getServiceLocator()->get('viewpdfrenderer')->getHtmlRenderer()->render($pdf);
$eng    = $this->getServiceLocator()->get('viewpdfrenderer')->getEngine();

$eng->load_html($html);
$eng->render();

Will fail, however despite the answer being very hard to find online the solution is rather simple, simply use the html renderer but request dompdf from the service manager, below I will render multiple PDF’s with different views, save them as files ready to be attached to an email.

        // first PDF
        $pdf = new PdfModel();
        $pdf->setTerminal(true);
        $pdf->setTemplate('template1');
        $pdf->setVariables(array(
          'foo'         => 'bar'
        ));

        $html                   = $this->getServiceLocator()->get('viewpdfrenderer')->getHtmlRenderer()->render($pdf);
        $dompdf                 = $this->getServiceLocator()->get('dompdf'); // get fresh instance everytime

        $dompdf->load_html($html);
        $dompdf->render();
        file_put_contents('file1.pdf', $dompdf->output());




        // second pdf
        $pdf = new PdfModel();
        $pdf->setTerminal(true);
        $pdf->setTemplate('template2');
        $pdf->setVariables(array(
          'foo'         => 'bar'
        ));

        $html                   = $this->getServiceLocator()->get('viewpdfrenderer')->getHtmlRenderer()->render($pdf);
        $dompdf                 = $this->getServiceLocator()->get('dompdf'); // get fresh instance everytime

        $dompdf->load_html($html);
        $dompdf->render();
        file_put_contents('file2.pdf', $dompdf->output());

Happy coding!