Object oriented programming (OOP) was first introduced in php4. Area for oop in php version 4 was not very vast. There were only few features available in php4. Major concept of the object oriented programming in PHP is introduced from version 5(we commonly known as php5). Also php community has plan to modify its object model structure in more better manner in php6(not released yet). But still in php5 object model is designed nicely. If you have good understanding of OOP then you can create very good architecture of your php application. You only need to know some of the basic principles of object oriented programming and how to implement that concept of oop in php.
Class − This is a programmer-defined data type, which includes local functions as well as local data. You can think of a class as a template for making many instances of the same kind (or class) of object.
Object − An individual instance of the data structure defined by a class. You define a class once and then make many objects that belong to it. Objects are also known as instance.
Inheritance − When a class is defined by inheriting existing function of a parent class then it is called inheritance. Here child class will inherit all or few member functions and variables of a parent class.
Polymorphism − This is an object oriented concept where same function can be used for different purposes. For example function name will remain same but it make take different number of arguments and can do different task.
Data Abstraction − Any representation of data in which the implementation details are hidden (abstracted).
Encapsulation − refers to a concept where we encapsulate all the data and member functions together to form an object.
