PHP OOP Inheritance

PHP OOP Inheritance

PHP OOP Inheritance allows a class (child) to take properties and methods from another class (parent).

Parent class = Base class (super class)
Child class = Derived class (sub class)

Why Use Inheritance?

Reuse code
Avoid duplication
Create hierarchical structure
Extend existing functionality
Used heavily in Laravel controllers & models

Basic Inheritance Example

Child Class Adds Its Own Features

class ParentClass {
public function message() {
echo "I am Parent";
}
}

class ChildClass extends ParentClass {
public function extra() {
echo "I am Child";
}
}

$obj = new ChildClass();
$obj->message(); // From Parent
$obj->extra(); // From Child

class ParentClass {

public function message() {

echo "I am Parent";

}

class ChildClass extends ParentClass {

public function extra() {

echo "I am Child";

}

$obj = new ChildClass();

$obj->message(); // From Parent

$obj->extra(); // From Child

Child Class Overriding Parent Method (Very Important)

Child class can replace a parent method.

Using parent:: to Call Parent Method

Inheritance with Properties

Constructor in Inheritance

Parent constructor auto runs when creating child object:

Output:

Parent constructor does not run automatically if overridden.

To run both:

Protected with Inheritance

Protected properties/methods can be used inside child class:

Real-Life Practical Example

Parent Class: Vehicle

Child Classes:

class Car extends Vehicle {
public function wheels() {
echo "Car has 4 wheels<br>";
}
}

class Bike extends Vehicle {
public function wheels() {
echo "Bike has 2 wheels<br>";
}
}

$c = new Car();
$c->start();
$c->wheels();

$b = new Bike();
$b->start();
$b->wheels();

class Car extends Vehicle {

public function wheels() {

echo "Car has 4 wheels<br>";

}

class Bike extends Vehicle {

public function wheels() {

echo "Bike has 2 wheels<br>";

}

$c = new Car();

$c->start();

$c->wheels();

$b = new Bike();

$b->start();

$b->wheels();

Summary Table

Term	Meaning
Parent class	Base class
Child class	Inherits from parent
extends	Used to implement inheritance
Overriding	Child replaces parent method
parent::	Calls parent method/constructor

PHP OOP Inheritance