How to get a page count in an mPDF document?

You can use {nbpg}, like

<div align="center"><b>{PAGENO} / {nbpg}</b></div>

I was looking for the same functionallity while using EYiiPdf (a wrapper for mPDF on Yii) and the following worked like a charm:

$mPDF->setFooter('{PAGENO} / {nb}');

I checked mPDF's source and found this at mpdf.php:1656 (version 5.4):

function AliasNbPages($alias='{nb}') {
    //Define an alias for total number of pages
    $this->aliasNbPg=$alias;
}

Hope it helps!

If you are trying to return the number of pages so you can save this to a database or some other operation outside of mpdf it's easy to pull it this way.

After you write your content:

$mpdf->WriteHTML($html);
$page_count = $mpdf -> page;

$mpdf->Output();