PHP mPDF PDF checkboxes checked

Disclaimer: Knows nothing about mPDF :(

I am creating a PDF using mPDF , I was able to get the table printed successfully. I am having some problems when it comes to validating my checkboxes. Checkboxes are not checked in PDF, but if I view the same code in HTML, it is checked. eg

$output .= '<td width="50%" colspan="2">';
  $output .= '<strong>Instructed Another Solicito?</strong> ';
  $output .= 'Yes <input type="checkbox" checked /> ';
  $output .= 'No &nbsp; <input type="checkbox" />';
$output .= '</td>';

      

        
        
        
      

    

If I view them in HTML echo $output;

, yes, it will be checked, but as soon as I post the PDF file i.e. $mpdf->WriteHTML($html); $mpdf->Output();

will be shown as unverified.

What do I need to do to check my checkboxes is there any other way to get this

Any idea?