Do you know any PHP framework for a Q&A system with upvoting, just like this one at PH?

The PHPJabbers folks (https://www.phpjabbers.com/) have a lot of php scripts - they might have one. If your site is based on WordPress there are a few Q&A plugins there as well.

Ooooh I would be interested in that too.

Yes, You get more information about PHP framework here www.dumpsschool.com