If that could be the first of OOP serie here that would be awesome.
There is still lots of material to write about and to be honest it's very difficult to find such a clean and easy to understand explanation of all those concepts.
Hope you will continue with for example that:
There are also other interesting OOP features like constructor and destructor functions, access protection modifiers, static functions and variables, etc.. but I do not want to go there. This is enough to get you started and migrate your global code to OOP PHP classes.