> How to overcome this?
You start with branching out to actually different programming languages. If you already know PHP, don't go and learn Java or C#, you basically already know those from PHP, you're only missing knowledge of the public API (what methods should be called when, naming conventions) and so on.
Instead, seek languages that when you see them the first time you say "wow, I don't understand anything" and sit down and try to learn one of those. For me, Clojure was always one of those languages that kindled the "what the hell is that" feeling in me, but after reading a lot of praise for the language, I started learning it anyways.
Now I work on Clojure(Script) code full-time, and programming is finally a fun thing to do again.
I won't try to learn Common Lisp or anything like that next, as I know that if I spent the time, it'd be easy, it's just Clojure but with different functions to call, different conventions, but mostly the same. So the next language I'm targeting is Rust. A C-like language, but new concepts around the borrow-checker and lifetimes, something I've been exposed to before, but not this literally.