The function offsetGet raises a warning for PHP 8

[meljturner]

There is an incompatibility with PHP 8.1.

Temporary fix is to add attribute:

#[\ReturnTypeWillChange]  at line 140 in Dom/Collection.php

[rgex]

There are many issues with this library which isn't maintained anymore.
The only good news is that with PHP 8.4 we will get a decent native DOM parser in a couple of months.
https://wiki.php.net/rfc/domdocument_html5_parser