There are more important things about OOP

There are more important features on the object oriented programming wich haven't been discused on the text.

One of them is the class heritage which makes you to save a lot of lines of code while maintaining the code complexity.

Furthermore, with a few knowledges of oop, you can create some sort of design patterns like the Singleton wich needs the private and static modifiers.

Right, but as it was explained in the article and it was repeated several times in the comments, that was outside of the scope of this article.

The scope of the article was just about letting people that do not use OOP in PHP the main difference between global code and object oriented code, which is encapsulation.

Covering all advantages of object oriented programming would take a very long article and there are plenty of articles out there doing that already.