PHP Inheritance: Reuse Code with Extends

What is it?

Inheritance lets a child class reuse all the code of a parent class and add or override behaviour. The parent holds shared logic; children specialise it.

Why does it matter?

Without inheritance you would duplicate shared logic across every class. A Dog and Cat class both eat and sleep — put that in an Animal parent class and inherit it rather than duplicating it.

Learn PHP inheritance — child classes extend parents, override methods, and call parent:: .

Real-World Use Cases

🐾 Animal taxonomy - Animal parent → Dog, Cat, Bird children each inherit eat() and sleep() but override makeSound().
👤 User roles - User parent → AdminUser, GuestUser children that inherit getProfile() but override getPermissions().
💳 Payment methods - Payment parent → CreditCard, UPI, NetBanking children that share processRefund() but override pay().
📄 Document types - Document parent → Invoice, Receipt, PurchaseOrder children sharing a header/footer but different body templates.

Parent and Child Class

<?php

/*
--------------------------------
Parent and Child Class in PHP
(Inheritance)
--------------------------------
*/

// Parent Class
class Animal {

    public $name;

    public function eat() {

        echo $this->name . " is eating.<br>";
    }
}

// Child Class
class Dog extends Animal {

    public function bark() {

        echo $this->name . " is barking.<br>";
    }
}

// Create Object
$dog = new Dog();

// Access Parent Property
$dog->name = "Tommy";

// Access Parent Method
$dog->eat();

// Access Child Method
$dog->bark();

?>

Overriding Methods

<?php

/*
--------------------------------
Method Overriding in PHP
--------------------------------
*/

// Parent Class
class Animal {

    public function sound() {

        echo "Animal makes a sound.<br>";
    }
}

// Child Class
class Dog extends Animal {

    // Override Parent Method
    public function sound() {

        echo "Dog barks.<br>";
    }
}

// Another Child Class
class Cat extends Animal {

    // Override Parent Method
    public function sound() {

        echo "Cat meows.<br>";
    }
}

// Objects
$animal = new Animal();
$dog = new Dog();
$cat = new Cat();

/*
--------------------------------
Call Methods
--------------------------------
*/

$animal->sound();

$dog->sound();

$cat->sound();

?>

Calling the Parent with parent::

<?php

/*
--------------------------------
Calling Parent Method using parent::
--------------------------------
*/

// Parent Class
class Animal {

    public function sound() {

        echo "Animal makes a sound.<br>";
    }
}

// Child Class
class Dog extends Animal {

    // Override Method
    public function sound() {

        // Call Parent Method
        parent::sound();

        // Child Class Code
        echo "Dog barks.<br>";
    }
}

// Object
$dog = new Dog();

/*
--------------------------------
Call Method
--------------------------------
*/

$dog->sound();

?>

Q: Can a child class have multiple parent classes in PHP?

No. PHP supports single inheritance only. Use interfaces for contracts and traits for code reuse across unrelated classes.