A class can be anywhere, but it is convention (and helps in organisation) to have each class in its own file. You can have a class intermingled with your code but this sort of defeats the purpose.

Yes, you have many classes. Say one to deal with users and a class for products that lets you create an object for each product.

If you had an online shop, you could have a class that creates objects for each item. Each item has properties (price, name, availability) and methods (changePrice, checkAvailability).

Once you have set up the methods, you can call them and they take all of the processing out of the script that's outputting their data......

Ummmm.. an anolgy for OOP abstraction is this.

Your computer hardware is the base of your computer heirachy the next level up in this abstraction is the operating system kernel , then the hardware device drivers followed by applications running on your operating system.

When you write a computer program, it would be very hard to have to write the code to deal with the hardware primitives for everything. Instead, the program takes advantage of object libraries in the operating system (which in turn deals with the drivers objects that deal with the hardware) allowing the end program to just asks for those results.

This is why programs generally cannot be used on different operating systems as they are tapping into the objects set up for a given system. The program doesn't have to worry about the fiddly bits and can just use the results of the abstraction to perform its functions.

I hope I am making sense. OOP doesn't allow you to do anything more than what you can do normally, it just allows you to do it in a more ergonomical, logical way.

It's a way of mind

*** Rakulie stops himself before saying "very good grasshopper" ***