Inheritance

Ever felt like you’re rewriting the same logic over and over in your PHP classes? Maybe it’s the same properties or methods that just keep popping up. Here's where PHP inheritance steps in to avoid that.

With inheritance, you can set up shared behaviors in one place—so your code is more streamlined, less repetitive, and, most importantly, easier to manage.

In the next sections, you will learn how PHP inheritance can help you write cleaner, simpler code without all the repetition.

What is PHP Inheritance?

Generally, inheritance is a way for one class to gain the properties and methods of another. So if you have a class called Vehicle with properties like $wheels and $engine. Instead of creating a Car class and retyping those same properties, you can set up Vehicle as a parent class. Then, Car can inherit all that useful info directly from Vehicle without duplicating code.

This lets you define shared traits in one place, saving you from repeating yourself and keeping things organized.

Inheritance creates a structure where the parent class holds common traits, while child classes use and expand upon those traits as needed.

In the following example, you will learn how to write inheritance in PHP:

class ParentClass {
    public $property;

    public function method() {
        // Code here
    }
}

class ChildClass extends ParentClass {
    // Additional properties or methods specific to ChildClass
}

In this setup:

The “extends” keyword is the key to inheritance, telling PHP that ChildClass should inherit everything in ParentClass.

Anyway, In the below section, you’ll see how to set up inheritance in PHP.

Setting Up Inheritance in PHP

Consider you are creating a system that manages different kinds of vehicles. You might start with a Vehicle class:

class Vehicle {
    protected $wheels;
    protected $engine;

    public function __construct($wheels, $engine) {
        $this->wheels = $wheels;
        $this->engine = $engine;
    }

    public function startEngine() {
        return "Engine started";
    }
}

Now, if you want to create specific vehicle types like Car or Bike, these classes can be inherited from Vehicle:

class Car extends Vehicle {
    public function drive() {
        return "Car is driving with " . $this->wheels . " wheels.";
    }
}

class Bike extends Vehicle {
    public function pedal() {
        return "Bike is pedaling with " . $this->wheels . " wheels.";
    }
}

So, Car and Bike inherit the properties $wheels and $engine, as well as the startEngine() method from Vehicle. This structure is tidy, prevents repetitive code, and allows each class to add its unique traits.

You are now seeing how inheritance can simplify your code and improve the code readability. In the following section, you will learn the types of inheritance in PHP and which one you have to use.

Types of PHP Inheritance and Which One Do You Need?

PHP primarily supports single inheritance. This means a class can inherit from only one parent class, which can sometimes feel limiting. But don’t worry—PHP offers two ways to work around this if you need more flexibility:

Each of these options provides a way to tailor your code structure based on what you are trying to achieve.

In the next section, let’s bring it all together with some examples.

Example of PHP Inheritance

Here, we can take our Vehicle example and expand it to show how inheritance plays together.

class Vehicle {
    protected $engine;
    public function startEngine() {
        return "Starting engine...";
    }
}

class Car extends Vehicle {
    public function honk() {
        return "Honk! Honk!";
    }
}

class Motorcycle extends Vehicle {
    public function revEngine() {
        return "Revving engine!";
    }
}

In this example, the Car and Motorcycle both inherit from Vehicle, but each adds something unique—honk() for Car and revEngine() for Motorcycle. This way, you maintain shared functionality in Vehicle, while each child class focuses on its specific behavior.

Anyway, let's summarize it.

Wrapping Up

PHP inheritance lets you share common properties and methods across different classes, saving you time and simplifying your code. Here is a quick summary of the basics:

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