By PHP Manual Prev Next Chapter 13. A class is a collection of variables and functions working with these variables.
Classes are types, that is, they are blueprints for actual variables.
You have to create a variable of the desired type with the new operator. Classes can be extensions of other classes. The extended or derived class has all variables and functions of the base class and what you add in the extended definition. This is done using the extends keyword. Multiple inheritance is not supported.