What Is Object-Oriented Programming?

So far you have written code as a list of steps, with variables and functions. That style is called procedural programming, and it works well for small scripts.

As a project grows, you find yourself passing the same group of values around: a user’s name, email, role and ID. Object-oriented programming (OOP) keeps related data and the code that works on it together in one unit, called an object.

A picture: a car

A real car has:

• Properties (data): colour, speed, fuel level.
• Actions (behaviour): accelerate, brake, refuel.

An object in code is the same: it has properties and methods.

Procedural vs object-oriented

The same small task in two styles:

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<?php
// Procedural: data and functions are separate
$user = ["name" => "Isha", "email" => "isha@example.com"];

function greetUser(array $user): string
{
    return "Hello, " . $user["name"];
}

echo greetUser($user) . "\n";

// Object-oriented: data and behaviour live together
class User
{
    public function __construct(
        public string $name,
        public string $email,
    ) {}

    public function greet(): string
    {
        return "Hello, " . $this->name;
    }
}

$user = new User("Isha", "isha@example.com");

echo $user->greet();

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Hello, Isha
Hello, Isha

The result is the same. The difference shows when the project grows: a User always has a name and an email, and everything you can do with a user is in one place.

The four ideas of OOP

You will meet these in the next lessons.

Why use OOP

• Organisation. Code is split into small, named pieces.
• Reuse. One class can be used in many places.
• Safety. Objects can protect their data and keep it valid.
• Teamwork. Frameworks and libraries are built from classes, so you need OOP to use them.

When not to use it

A ten-line script does not need a class. OOP is a tool for managing complexity. Use it when you have something with a clear identity and several related actions, such as a user, an order, a product or a database connection.

Where you will meet it

• Laravel and Symfony are built entirely from classes.
• WordPress uses classes in many places (WP_Query, WP_Post, widgets).
• Composer packages are almost always classes.