As a PHP developer, mastering Object-Oriented Programming (OOP) is essential for writing scalable, maintainable, and efficient applications. OOP principles help us structure our code better, making it easier to extend and debug. In this blog, I’ll go over the core OOP principles and share my personal take on why they matter.

I don't want to be a teacher here, but since I will finish uni in June 2025, I think I can give my opinion. I also use these principles when designing new systems or refactoring them.

What Are OOP Principles?

Object-Oriented Programming is based on four fundamental principles:

Encapsulation
Abstraction
Inheritance
Polymorphism

These principles help organize code into reusable and modular components, reducing complexity and improving maintainability.

1. Encapsulation

Definition: Encapsulation means bundling data (variables) and methods (functions) into a single unit (class) while restricting direct access to some of the object's components.

Example:

class User {
    private $name;

    public function setName($name) {
        $this->name = $name;
    }

    public function getName() {
        return $this->name;
    }
}

$user = new User();
$user->setName("Cristian");
echo $user->getName(); // Output: Cristian

My Opinion: Encapsulation is one of my favorite OOP concepts because it keeps the data secure and prevents accidental modifications. It also makes code more readable and predictable.

2. Abstraction

Definition: Abstraction allows us to hide complex implementation details and expose only the relevant parts of an object’s behavior.

Example:

abstract class Animal {
    abstract public function makeSound();
}

class Dog extends Animal {
    public function makeSound() {
        return "Bark!";
    }
}

$dog = new Dog();
echo $dog->makeSound(); // Output: Bark!

My Opinion: Abstraction helps a lot when working with large codebases. It allows us to focus on what an object does rather than how it does it, which makes development faster and cleaner.

3. Inheritance

Definition: Inheritance allows one class to derive properties and behaviors from another class, promoting code reuse.

Example:

class Vehicle {
    public function start() {
        return "Vehicle started";
    }
}

class Car extends Vehicle {
    public function drive() {
        return "Car is driving";
    }
}

$car = new Car();
echo $car->start(); // Output: Vehicle started

My Opinion: Inheritance is great, but it should be used carefully. If misused, it can lead to tightly coupled code, making future modifications harder.

4. Polymorphism

Definition: Polymorphism allows objects of different classes to be treated as objects of a common super class. It helps in designing flexible and extensible code.

Example:

interface PaymentMethod {
    public function pay($amount);
}

class PayPal implements PaymentMethod {
    public function pay($amount) {
        return "Paying $amount via PayPal";
    }
}

class CreditCard implements PaymentMethod {
    public function pay($amount) {
        return "Paying $amount via Credit Card";
    }
}

function processPayment(PaymentMethod $payment, $amount) {
    echo $payment->pay($amount);
}

processPayment(new PayPal(), 100); // Output: Paying 100 via PayPal

My Opinion: Polymorphism is one of the most powerful OOP principles because it allows us to design systems that are flexible and scalable. It’s a must-have for building complex applications.

Final Thoughts

Understanding and applying these OOP principles correctly will help you write cleaner and more maintainable code. While some developers might prefer procedural programming, I find OOP much more structured and efficient, especially for large projects.

If you're not using OOP yet, I highly recommend giving it a try. Once you get the hang of it, you'll see a massive improvement in your code quality.

Understanding Object-Oriented Programming (OOP) Principles in PHP