Notice warnings

If you get something like:

Notice: Undefined index: win-1252 in src/Mpdf.php on line 3741

you might need to suppress NOTICE warnings using e.g.

<?php
$former = error_reporting(E_ALL ^ E_NOTICE);

// or

$former = error_reporting(0);

Include this at the start of your script before instantiating and running mPDF.

It is a good practice to return the former error_reporting after

<?php
error_reporting($former);

Also, you could want to report the notice in the mPDF Github issue tracker