__invoke is just for making a class Callable. Java has those with functional interfaces. __get is just dynamic property resolution synax sugar. Instead of something like obj.get("property") you do obj->property.

Instead, I would like to see ADTs, generics, pattern matching, immutability, expressions everywhere and a better stdlib. Then one could call PHP functional.

It's like how people say Javascript is functional. Sure, it has lambdas, anonymous functions, closures, const. But those alone don't make it functional.

Functional programming is very different (and at times hard). If you have the time you can check out F#, OCaml, Elixir, Erlang, Rust or Haskell (in order of difficulty imo). Those are more "pure" functional, rather than imperative/OOP with a touch of functional.

See how things work, what features they have and don't have. How problems are solved in these languages. I think learning about one of them can give you a different perspective on what functional means. I discovered F# one day, got curious and discovered a whole different paradigm, a new perspective on programming. And learning about functional programming really made me a better programmer, even on procedural/OOP.