Many requests sent to me to write ideas and more explanations about PHP OOP and Classes, while they experience defficulties understanding the power and the reason using OOP.

Let me start with: 

Why to use OOP?
When we start writing code, we use functions. Most programmers know functions and the use of them.
Let me give you an example, to use it in functions then in OOP.

I will use Database Connection as an Example.