Polymorphism in PHP

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Another principle that is key to Object Oriented Programming is Polymorphism. Polymorphism in PHP means “many forms”. This is just a simple way of saying that the same method name can take different forms in different classes.

Due to polymorphism, you will be able to write flexible and reusable code. The result is that your application will be easier to extend and maintain.

What Is Polymorphism in PHP

Polymorphism is an objects response to the same method can be different depending on the class.

It follows that:
You may use one interface
But get different results

In PHP the mechanism of polymorphism is
method overriding
interfaces
abstract classes

Method Overriding in PHP

Overriding a method is one of the ways to obtain a polymorphy. In this case child class should define a method which has a same name and functional characteristic as the parent has.

Example of Method Overriding

class Animal {
    public function sound() {
        echo "Animal sound";
    }
}

class Dog extends Animal {
    public function sound() {
        echo "Dog barks";
    }
}

class Cat extends Animal {
    public function sound() {
        echo "Cat meows";
    }
}

$dog = new Dog();
$cat = new Cat();

$dog->sound();
$cat->sound();

Explanation

All of the classes use the same method name sound().
But every different class gives a different answer
This is polymorphism in action.

Polymorphism Using Interfaces in PHP

Interfaces also enable polymorphism. They specify methods that classes have to implement.

Interface Example

interface Payment {
    public function pay();
}

class CardPayment implements Payment {
    public function pay() {
        echo "Paid by card";
    }
}

class UpiPayment implements Payment {
    public function pay() {
        echo "Paid using UPI";
    }
}

function processPayment(Payment $payment) {
    $payment->pay();
}

processPayment(new CardPayment());
processPayment(new UpiPayment());

Explanation

Interfaces also enable polymorphism. They specify methods that classes have to implement.
So, you will be able to add new payment types without modifying the function.

Why Polymorphism Is Important in PHP

Polymorphism increases flexibility.

It helps you
Write reusable & maintainable code
Limit condition statements
Easily extending applications

For these reasons, big projects rely on polymorphism.

Real World Example

Imagine a remote control.

You use the same on/off button.
But it is works on other devices also.

Similarly, polymorphism enables a method to have multiple behaviors.

Common Use Cases of Polymorphism

Payment systems
Notification systems
User role handling
API integrations

Though the systems need some flexibility then polymorphism can be used effectively.

Polymorphism vs Method Overloading

Unlike in many other languages where it is possible to overload methods, in PHP it is not, but there are ways to emulate this feature.

Summary

Polymorphism involves identifying the same task or action performed by PHP objects with the same method name. It uses method overriding, interfaces and abstract classes. Utilizing the power of polymorphism ensures you design highly flexible, scalable and maintainable Object Oriented PHP applications.