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PHP OOP (Object-Oriented Programming)

 

PHP is not only for writing simple scripts — it also supports Object-Oriented Programming (OOP). OOP helps you structure code into classes and objects, making applications more organized, reusable, and easier to maintain.

✅ What is OOP?

In simple terms:

  • Class → A blueprint (like a design or template).
  • Object → A real thing created from the class (like an actual car made from the blueprint).

OOP groups related properties (data) and methods (functions) together, instead of writing scattered functions.

🔑 Core OOP Concepts in PHP

1. Class and Object

A class is a blueprint, and an object is an instance of that class.

<?php

// Define a class

class Car {

    public $brand;

    public $color;

 

    public function drive() {

        echo "The car is driving!";

    }

}

 

// Create an object

$myCar = new Car();

$myCar->brand = "Toyota";

$myCar->color = "Red";

 

echo $myCar->brand; // Output: Toyota

$myCar->drive();    // Output: The car is driving!

?>

2. Constructor (__construct)

Constructors automatically run when an object is created.

<?php

class Car {

    public $brand;

 

    public function __construct($brand) {

        $this->brand = $brand;

    }

}

 

$car1 = new Car("Honda");

echo $car1->brand; // Output: Honda

?>

3. Inheritance

A class can inherit properties and methods from another class.

<?php

class Vehicle {

    public $speed = "100 km/h";

 

    public function move() {

        echo "The vehicle is moving.";

    }

}

 

class Car extends Vehicle {

    public function honk() {

        echo "Beep! Beep!";

    }

}

 

$myCar = new Car();

echo $myCar->speed; // Inherited property

$myCar->move();     // Inherited method

$myCar->honk();     // Car's own method

?>

4. Encapsulation (Access Modifiers)

You can control access to class properties/methods with:

  • public → Accessible everywhere.
  • protected → Accessible only in the class and subclasses.
  • private → Accessible only inside the class.

<?php

class BankAccount {

    private $balance = 0;

 

    public function deposit($amount) {

        $this->balance += $amount;

    }

 

    public function getBalance() {

        return $this->balance;

    }

}

 

$account = new BankAccount();

$account->deposit(500);

echo $account->getBalance(); // Output: 500

?>

5. Polymorphism

Different classes can have methods with the same name, but different behavior.

<?php

class Animal {

    public function sound() {

        echo "Some sound";

    }

}

 

class Dog extends Animal {

    public function sound() {

        echo "Bark!";

    }

}

 

class Cat extends Animal {

    public function sound() {

        echo "Meow!";

    }

}

 

$dog = new Dog();

$cat = new Cat();

 

$dog->sound(); // Output: Bark!

$cat->sound(); // Output: Meow!

?>

6. Interfaces & Abstract Classes

  • Abstract classes provide a base but cannot be instantiated directly.
  • Interfaces define methods that must be implemented in classes.

<?php

// Interface

interface PaymentGateway {

    public function pay($amount);

}

 

// Class implementing interface

class PayPal implements PaymentGateway {

    public function pay($amount) {

        echo "Paid $amount using PayPal.";

    }

}

 

$payment = new PayPal();

$payment->pay(100);

?>

🎯 Benefits of OOP in PHP

  • Code is reusable (inheritance, interfaces).
  • Projects are easier to maintain.
  • Encapsulation secures sensitive data.
  • Makes applications more scalable and organized.

 

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