Where to start?

[Robust]

Where did you start in learning PHP? I want to learn it mainly for XenForo, but also perhaps for general use too in the future.

I'm familiar with some of it, and developed MyBB plugins but they were much simpler, XenForo is a much more complex system just importing it into my IDE.

 

[LPH]

I learned the majority from the awesome developers here and reading the XenForo code. Read the code from the other developers too.

XenForo Tutorials:
https://xenforo.com/community/resources/categories/development-tutorials.36/

General OOP with videos:
http://www.killerphp.com/tutorials/object-oriented-php/