Up to version 9.3.4 and possibly future 9.4.x, ProjeQtOr is not compatible with PHP 8.1.
Some backwards-compatibility breaking change brought by PHP 8.1 will raise "Deprecated" warnings.
Avoid deploying PHP 8.1 or be sure to remove deprecation noitices.
It would be really great if this were mentioned in the installation instructions here: https://www.projeqtor.org/files/readme.txt
I spent several hours yesterday installing ProjeQtOr V9.4.3 in a custom Docker configuration, and about 30 minutes of that was debugging why it wouldn't work on a production setup even though my initial prototype worked fine.
I tracked it down to the using the standard php:8-apache container, which has PHP 8.1. I searched the web for the error message I was getting and found a form post about ProjeQtOr being incompatible with PHP 8.1. I went back and changed my containers to be based on php:8.0-apache and this solved the problem completely.
Anyway, not a huge deal, I have no problem running with any version of PHP that works (containerization makes that very easy), but I wish I had known about it up front. =)
Thanks for making such a great piece of software.
Same issue yesterday
Here is the compatibility matrix for versions of ProjeQtOr, PHP and MySQL, and various technical requirements :
https://www.projeqtor.org/en/product-en/technical-en/64-setup-en/412-product-prerequisites-en