PHP Polymorphism: Complete Guide with Examples

1. Introduction

Polymorphism is an important concept in Object-Oriented Programming (OOP). In simple words, polymorphism means one name, many forms.

The word Polymorphism comes from two Greek words:

• Poly → meaning many
• Morph → meaning forms

In PHP, polymorphism allows different classes to use the same method name but perform different actions. This is very useful when multiple classes share a common interface but need different implementations.

2. Syntax

In PHP, polymorphism is usually implemented using interfaces or inheritance.

Basic syntax using an interface:

interface InterfaceName {
   public function methodName();
}

class ClassOne implements InterfaceName {
   public function methodName() {
       // implementation
   }
}

class ClassTwo implements InterfaceName {
   public function methodName() {
       // different implementation
   }
}

Here:

• The interface defines a common method.
• Multiple classes implement that interface.
• Each class provides its own implementation of the method.

3. Example

In this example, both Apple and Orange classes implement the same interface method taste(), but each class returns a different result.

interface Fruit {
   public function taste();
}

class Apple implements Fruit {

   public function taste() {
       return "Apple taste is very sweet.";
   }

}

class Orange implements Fruit {

   public function taste() {
       return "Orange taste is very sour.";
   }

}

$apple = new Apple();
echo $apple->taste();

echo "<br>";

$orange = new Orange();
echo $orange->taste();

Output:

Explanation:

Let’s understand how polymorphism works in the fruit example.

First, we created an interface called Fruit. An interface defines a method that must be implemented by any class that uses it.

interface Fruit {
   public function taste();
}

Next, we created two classes:

• Apple
• Orange

Both classes implement the Fruit interface using the implements keyword.

class Apple implements Fruit

Inside each class, we defined the taste() method, but the implementation is different.

For example:

Apple class:

return "Apple taste is very sweet.";

Orange class:

return "Orange taste is very sour.";

After that, we created objects of both classes.

$apple = new Apple();
$orange = new Orange();

When we call the taste() method, each object executes its own version of the method.

echo $apple->taste();
echo $orange->taste();

Even though the method name is the same, the behavior is different. This is exactly what polymorphism means.

4. Real-world Example

Let’s understand polymorphism with a real-world payment system example.

In an online shopping website, users can pay using different methods

• Credit Card
• PayPal
• UPI

Even though the payment process is different, all payment methods follow a common pay() method.

interface Payment {
   public function pay($amount);
}

class CreditCard implements Payment {

   public function pay($amount) {
       echo "Paid $" . $amount . " using Credit Card.";
   }

}

class UPI implements Payment {

   public function pay($amount) {
       echo "Paid $" . $amount . " using UPI.";
   }

}

$payment1 = new CreditCard();
$payment1->pay(100);

echo "<br>";

$payment2 = new UPI();
$payment2->pay(200);

In this example:

• The Payment interface defines the pay() method.
• Different classes implement the method differently.
• The same method name performs different tasks.

This is a perfect example of polymorphism in real applications.

Output:

8. Conclusion

PHP polymorphism is a powerful feature of Object-Oriented Programming that allows the same method name to perform different tasks depending on the class that implements it.

In real-world applications such as payment systems, notification services, and API integrations, polymorphism plays a key role in designing scalable and clean code architecture.

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