Add support for PHP 8s nullsafe operator.

[j-applese3d]

I'm not sure that I got everything right, so please review and let me know what I need to change :)

For instance the test will fail if you run it with PHP <8.0, and I wasn't certain that specific test file was the right one to update or if I should make a new one. I didn't know where to put it...

Thanks! Related Issue: #633