This is really cool to hear as someone who used to experiment with Haxe for game development. Would love to read a case study.

We started small. And prototyped with just a single feature.

Basically we generate code in our src folder under a reserved namespace, and other PHP code can then use that code with imports. As we grow, we might want to split this into separate compilation units (we are not there yet, as the Haxe compiler is really fast!)

At the moment the generated PHP code is checked in source control, again we might want to have this done in CI, but it works kind of nicely at the moment.

The tricky bits are how to "speak" to PHP. Haxe is a really nice functional language (even its syntax is traditionally class based, but you can have module level fields in Haxe since 2020), so its pretty annoying to handle option types etc from the PHP side. We are still not decided on this part, and many APIs expose duplicate functions for some general task, like foo and foo_exn, and the one that ends with _exn throws instead of returning a variant (like option/maybe etc)

Also, its tricky to design where data is fetched from. We tend to keep the Haxe code as pure as possible, and only taking input and returning output (not doing any IO). We also write our own typings for externals, this has actually been really good for us, as we can observe easily what we actually use, and if we can remove some dependency that has some one feature we only use.

Overall, im amazed not more PHP devs look into Haxe as its basically a better version of what is TypeScript > JavaScript. Also there is no other compile to PHP language im aware of that ha the same robustness and features Haxe has.