class main in PHP file $_POST

Question

I arrived in a situation that gave a result a little confused here..

I have a. php file in which I have a class called main, if I urge this class main -> $main = new main the $_POST array that used to have some variables is empty, but if I change the class name to main*, that is to say, maind, mainc, or any other name. the $_POST is not reset, or if I read the variables before instantiating the main class, but after it is empty.

What’s happening when I urge the main class? am I overwriting any class that interferes with the $_POST?

Note: the main class I created myself, I nicknamed this name because I didn’t need to be specific.