Method Overriding

Part of the Object Oriented Programming section of Coddy's PHP journey — lesson 23 of 91.

Sometimes the inherited method from a parent class doesn't quite fit what the child class needs. Method overriding lets a child class provide its own implementation of a method that already exists in the parent.

To override a method, simply define a method in the child class with the same name as the parent's method:

<?php
class Animal {
    public $name;
    
    public function __construct($name) {
        $this->name = $name;
    }
    
    public function speak() {
        return "$this->name makes a sound";
    }
}

class Cat extends Animal {
    public function speak() {
        return "$this->name says meow";
    }
}

$cat = new Cat("Whiskers");
echo $cat->speak();

Output:

Whiskers says meow

The Cat class completely replaces the parent's speak() method with its own version. When you call speak() on a cat object, PHP uses the child's implementation.

You can also extend the parent's behavior by combining parent:: with your own logic:

<?php
class Dog extends Animal {
    public function speak() {
        return parent::speak() . " - woof woof!";
    }
}

$dog = new Dog("Rex");
echo $dog->speak();

Output:

Rex makes a sound - woof woof!

Key Point: Method overriding allows child classes to customize inherited behavior. You can completely replace a method or use parent:: to build upon the original implementation.

Challenge

Easy

Let's build a notification system that demonstrates how child classes can completely replace or extend parent methods through method overriding.

You'll create three files that work together to send different types of notifications, each with its own unique behavior:

Notification.php — Define a Notification class that serves as the base for all notification types. It should have a public $recipient property and a constructor that accepts and sets the recipient. Include a send($message) method that returns "Sending to [recipient]: [message]".
UrgentNotification.php — Define an UrgentNotification class that extends Notification. Include the Notification file at the top. This class should completely override the send($message) method to return "URGENT to [recipient]: [message]!!!" — notice the "URGENT" prefix and the exclamation marks at the end. This demonstrates fully replacing the parent's behavior.
LoggedNotification.php — Define a LoggedNotification class that extends Notification. Include the Notification file at the top. This class should override send($message) but build upon the parent's implementation: call parent::send($message) and append " [logged]" to the result. This demonstrates extending rather than replacing behavior.

In main.php, include all three notification class files. You'll receive two inputs: the recipient name and the message to send. Create one instance of each notification type (all using the same recipient), then call send() with the message on each one. Print each result on its own line in this order: regular notification, urgent notification, then logged notification.

This challenge shows both approaches to method overriding — the UrgentNotification completely replaces the parent's logic with its own formatting, while LoggedNotification uses parent:: to keep the original behavior and add to it.

Cheat sheet

Method overriding allows a child class to provide its own implementation of a method inherited from a parent class.

To override a method, define a method in the child class with the same name as the parent's method:

<?php
class Animal {
    public function speak() {
        return "makes a sound";
    }
}

class Cat extends Animal {
    public function speak() {
        return "says meow";
    }
}

The child class completely replaces the parent's method implementation. When called on a child object, PHP uses the child's version.

To extend the parent's behavior instead of replacing it, use parent:: to call the parent method and add your own logic:

<?php
class Dog extends Animal {
    public function speak() {
        return parent::speak() . " - woof woof!";
    }
}

This combines the parent's original behavior with additional functionality from the child class.

Try it yourself

<?php

require_once 'Notification.php';
require_once 'UrgentNotification.php';
require_once 'LoggedNotification.php';

// Read input
$recipient = trim(fgets(STDIN));
$message = trim(fgets(STDIN));

// TODO: Create one instance of each notification type (all using the same recipient)

// TODO: Call send() with the message on each notification
// Print each result on its own line in this order:
// 1. Regular notification
// 2. Urgent notification
// 3. Logged notification

?>

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Method Overriding

Cheat sheet

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