PHP Polymorphism Explained

Polymorphism is a fundamental notion in object-oriented programming (OOP) that allows objects of various classes to be considered as objects of the same superclass. Polymorphism in PHP is accomplished using inheritance and method overriding. Let me demonstrate how it works in PHP:

Inheritance:
In PHP, you can create a class that inherits properties and methods from another class. The derived class (also called subclass or child class) inherits the attributes and behaviors of the base class (also called superclass or parent class).

class Animal {
    public function makeSound() {
        return "Some generic sound";
    }
}

class Dog extends Animal {
    public function makeSound() {
        return "Woof!";
    }
}

class Cat extends Animal {
    public function makeSound() {
        return "Meow!";
    }
}

Here, we have a base class Animal with a method makeSound(), and two derived classes Dog and Cat, each of which overrides the makeSound() method with its own implementation.

Method Overriding:
In the example above, both Dog and Cat classes have a method called makeSound(), but they provide different implementations. This is known as method overriding. When you call makeSound() on an instance of Dog or Cat, it will invoke the respective method defined in the derived class, not the one in the parent class.

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

echo $dog->makeSound(); // Output: "Woof!"
echo $cat->makeSound(); // Output: "Meow!"

Polymorphism in Action: 
Polymorphism allows you to interchange objects of various classes as long as they share a common parent class. You might, for example, have an array of Animal objects and call makeSound() on each of them:

$animals = array(new Dog(), new Cat(), new Animal());

foreach ($animals as $animal) {
    echo $animal->makeSound() . PHP_EOL;
}

Output:

Woof!
Meow!
Some generic sound

In this example, we created an array containing objects of different classes (Dog, Cat, and Animal). Thanks to polymorphism, we can call the makeSound() method on each object without knowing its exact class. PHP automatically selects the appropriate method based on the actual class of the object at runtime.

This concept of polymorphism helps in writing flexible and extensible code in object-oriented PHP programs.

Hope you will understand.