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Introduction to Object Oriented Programming

Object Oriented Programming (OOP) is one of the most important concepts in modern software development.

Almost every large application today uses OOP.

Examples:

  • PocketMine-MP
  • Laravel
  • Symfony
  • WordPress
  • Discord Bots
  • Android Apps
  • Games
  • APIs
  • Enterprise Software

Why OOP Exists

Imagine building a server with:

  • Players
  • Worlds
  • Commands
  • Scoreboards
  • Economy
  • Friends
  • Parties

Without OOP:

$player1Money = 5000;
$player2Money = 10000;
$player3Money = 15000;

After 500 players:

$player527Money
$player928Money

Impossible to manage.

Real Life Example

Think about a Car.

A car has:

Properties:

Color
Brand
Speed
Fuel

Actions:

Start()
Stop()
Accelerate()
Brake()

This is exactly how OOP works.

OOP Terminology

Class​

Blueprint.

Example:

Player Blueprint

Object​

Actual instance created from blueprint.

Aayan
Steve
Alex

Property​

Variable inside class.

$name
$money
$rank

Method​

Function inside class.

sendMessage()
kick()
ban()

Visualization

Player Class
│
├── name
├── money
├── rank
│
├── sendMessage()
├── addMoney()
└── kick()

Objects:

Player1
Player2
Player3

Memory Representation

Class Definition
       ↓
new Player()
       ↓
Object Created
       ↓
Stored In Memory

Creating a Class

class Player {

}

Creating Object

$player =
new Player();

Creating Multiple Objects

$p1 = new Player();
$p2 = new Player();
$p3 = new Player();

Each object has its own memory.

Why OOP is Powerful

Code Reuse

Without OOP:

sendMessagePlayer1();
sendMessagePlayer2();
sendMessagePlayer3();

With OOP:

$player->sendMessage();

Better Organization

Projects become easier to understand.

Easier Teamwork

Multiple developers can work simultaneously.

Scalability

Large projects become possible.

Four Pillars of OOP

1. Encapsulation

Protect data.

Example:

private int $money;

2. Inheritance

Reuse existing classes.

Entity
   ↓
Human
   ↓
Player

3. Polymorphism

Same method can behave differently.

4. Abstraction

Hide internal implementation.

Example:

$database->connect();

You don't need to know how it works internally.

Procedural vs OOP

Procedural​

$name = "Aayan";

function kick() {

}

OOP​

$player->kick();

Example

Procedural:

function addMoney(
    &$money,
    int $amount
) {

    $money += $amount;

}

OOP:

$player->addMoney(
    1000
);

Cleaner and easier.

PocketMine Example

This:

$player->sendMessage(
    "Hello"
);

Internally:

Player Object
      ↓
Create Packet
      ↓
Serialize
      ↓
Send Through RakNet

This is abstraction.

Object Relationships

One Player belongs to one World​

Player
   ↓
World

One Server contains many Players​

Server
   ↓
Players[]

One Plugin contains many Commands​

Plugin
   ↓
Commands[]

OOP Architecture Example

Server
│
├── Players
├── Worlds
├── Commands
├── Scheduler
├── Network
└── Plugins

Everything is objects.

Enterprise Example

Controller
     ↓
Service
     ↓
Repository
     ↓
Database

Entire architecture is OOP.

Advantages

✅ Reusability

✅ Cleaner Code

✅ Easier Maintenance

✅ Better Team Development

✅ Better Architecture

✅ Scalable Projects

Disadvantages

❌ Slightly more difficult initially.

❌ More files.

❌ More abstraction.

Where OOP is Used

  • PHP Frameworks
  • PocketMine-MP
  • DragonFly
  • Java
  • C#
  • Unreal Engine
  • Android
  • APIs
  • Discord Bots
  • Enterprise Applications

Common Beginner Mistakes

Thinking Classes Store Data​

Classes are blueprints.

Objects store data.

Treating Objects Like Arrays​

Wrong:

$player["money"];

Correct:

$player->getMoney();

Everything Public​

Wrong:

public int $money;

Prefer:

private int $money;

Huge Classes​

Bad:

PlayerManager
5000 lines

Split responsibilities.

Exercises

Exercise 1​

Create blueprint:

Car

Properties:

brand
color
speed

Exercise 2​

Create blueprint:

Server

Methods:

start()
stop()
broadcast()

Exercise 3​

Think of real life objects and convert them into classes.

Mini Project

Design architecture:

Player
Party
Guild
Economy

How do these interact?

Quiz

What is a Class?​

Answer

Blueprint used to create objects.

What is an Object?​

Answer

Instance created from class.

Name four pillars of OOP.​

Answer

Encapsulation

Inheritance

Polymorphism

Abstraction

Real PocketMine Hierarchy

PluginBase
      ↓
Main

Entity
      ↓
Human
      ↓
Player

References

PHP OOP Documentation:

https://www.php.net/manual/en/language.oop5.php

Next Chapter

➡ Classes and Objects