Useful articles/books to get better as yii2 developer

Subject of topic says even more than expected about reason to open it.

Since some time i started to understand that you may be genius in your own closed world until someone will bring you something new to think about.

So lets become better together!

p.s. answers from high-rated users is welcome :)

If we’re talking about Yii specifics then the guide, website wiki pages, source code,

But overall, regardless of the framework, it helps to know OOP/OOD better (a check here is if you truly understand cohesion/coupling), HTTP protocol (RFC), PHP (manual), HTML (w3 spec), CSS (w3 spec), JavaScript (mozilla docs), security basics (