In my understanding, the class - this is the same as the object, in any case, PHP is a word synonymous.
So, the class - a few variables and functions combined in one structure responsible for specific action or transaction.
An example is the class for defining a search query, the class of the navigation menu, in a word set of functions and variables that will be very convenient to combine under one "roof".
That is, creating a variable of a class, you can easily access any variables or functions inside the class.
An example of a simple PHP class that shows how to construct php-class and how they work:
In programming classes in PHP5 there are many new, for example, now you can "protect" the functions and variables by simply adding them to the "protected", "private" or "public".
protected - protects a variable or a function of changes outside of the class or his heirs. That is, it can only be changed within a class and its descendants.
private - provides access to an item class only within the class in which the element is declared. , This is very useful if you are using proprietary code (Zen Optimizer or
something like that), for example, to check the activation code, shareware php-script.
public - Allows access to variable or function by any known methods and techniques.