Too many connections in MariaDB after CI and PHP upgrade

Actually, we did that, but then we realized that even with the old xampp, the same config in CI and the same credentials (that we left in a working copy in another Virtual Machine) the version 3.1.9 of CI didn't work either, and that we were able to connect to both databases with Navicat and PHPMyAdmin, using the project's credentials.

Moving back and forth with the system directory of CI 3.1.0 and 3.1.9 we were able to replicate the issue, and then we decide to left the database alone and focus on the project, since the logs of CI weren't showing anything useful. Applying the old-but-effective method of var_dump, log to file and echo we were able to isolate the problem in the load function of a library, and from that point on we started looking into the constructors, where we found the circular references. We solved that and up to now, everything seems to be working fine.

Best regards!