The problem is that newer versions are not working on the old php versions - we are staying somehow at a point where it would be the easiest solution to just split up the development with a v3 branch and a new v4 that is only compatible with php 7.1 (I guess will be the matching point where all libraries work on all new versions).

Another option would be to upgrade the packages only in travis (split the jobs to use different versions (with composer require phpunit:8.* for example).

Two dependencies are at fault: PHPUnit and PHP Code Sniffer.

PHPUnit starts spitting deprecated issues with 7.2 and PHP Code Sniffer with 7.4. I guess it is worth giving it a try with the latest versions of both dependencies in 7.4 and see how it reacts, not sure if the source will have to be edited to do so though. What do you think of doing this in a follow up PR to unblock this one?

Originally posted by @PierrickVoulet in #162 (comment)