What is Polymorphism in PHP? How to use Polymorphism?

Polymorphism is derived from two Greek words. Poly (meaning many) and morph (meaning forms). Polymorphism means many forms. In C you have two methods with the same name that have different function signatures and hence by passing the correct function signature you can invoke the correct method.

This is how polymorphism is achieved in languages like C where in a function sum(int, int) differs from sum(float, float). Therefore the method sum() has many forms depending on the parameters being passed to it.

The meaning with Object Oriented languages changes. With Object Oriented language polymorphism happens:
When the decision to invoke a function call is made by inspecting the object at runtime it is called Polymorphism

Why method polymorphism cannot be achieved
The reason why polymorphism for methods is not possible in PHP is because you can have a method that accepts two parameters and call it by passing three parameters. This is because PHP is not strict and contains methods like func_num_args() and func_get_arg() to find the number of arguments passed and get a particular parameter.
Because PHP is not type strict and allows variable arguments, this is why method polymorphism is not possible.

PHP 5 Polymorphism
Since PHP 5 introduces the concept of Type Hinting, polymorphism is possible with class methods. The basis of polymorphism is Inheritance and overridden methods.
Lets look at an example: Continue reading