monorepo-split-github-action VS unleash-client-php

In the latest version, he added the support for github and gitlab, so you can just include this as a workflow action and you are done for. This is awesome!

That's the point. You can, if GitHub Action is based on Dockerfile. I'm actually using the same Github Action https://github.com/symplify/monorepo-split-github-action for splitting repositories from Github and Gitlab :)

This is a nice feature to have, but doesn't have provide "repeatable randomness", meaning, if you want 10% of your users with the flag enabled, the same 10% should be selected every time. If you're A/B testing a new feature that spans multiple API endpoints, for example, all endpoints should be using the same feature. The Unleash library provides this functionality, however.

It's available at https://github.com/Unleash/unleash-client-php.

That's what projects like these are great for. I always release my packages for all currently supported versions. When I was writing unleash/client I didn't really want to write 7.3 code so I started researching my options. Long story short the code is written in PHP 8 but can be installed on 7.3+ thanks to Rector (though it was a little bumpy from time to time, but u/Tomas_Votruba and others from the team are really fast when there's an issue).