Alaa Amer

Object-Oriented Programming (OOP) in PHP - Detailed Guide

Object-Oriented Programming (OOP) in PHP - Detailed Guide

Specialized Guide by Alaa Amer – Professional Web & App Developer

Object-Oriented Programming (OOP) is a powerful programming paradigm that makes code more organized and maintainable. In PHP, OOP has evolved to become the foundation of modern frameworks.

2️⃣ Creating Basic Classes

<?php
class User {
    // Properties
    private $name;
    private $email;
    protected $age;
    public $isActive;

    // Constructor
    public function __construct($name, $email, $age) {
        $this->name = $name;
        $this->email = $email;
        $this->age = $age;
        $this->isActive = true;
    }

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

    public function setName($name) {
        if (strlen($name) >= 2) {
            $this->name = $name;
            return true;
        }
        return false;
    }

    public function getInfo() {
        return "Name: {$this->name}, Email: {$this->email}";
    }

    // Destructor
    public function __destruct() {
        echo "User deleted: {$this->name}";
    }
}

// Create object
$user1 = new User("Alaa Amer", "[email protected]", 30);
echo $user1->getInfo();
?>

4️⃣ Inheritance

// Base class
class Vehicle {
    protected $brand;
    protected $model;
    protected $year;

    public function __construct($brand, $model, $year) {
        $this->brand = $brand;
        $this->model = $model;
        $this->year = $year;
    }

    public function getInfo() {
        return "{$this->brand} {$this->model} ({$this->year})";
    }

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

// Inherited class
class Car extends Vehicle {
    private $doors;
    private $fuelType;

    public function __construct($brand, $model, $year, $doors, $fuelType) {
        parent::__construct($brand, $model, $year);
        $this->doors = $doors;
        $this->fuelType = $fuelType;
    }

    // Method Overriding
    public function start() {
        return "Car started with ignition key";
    }

    public function getCarDetails() {
        return $this->getInfo() . " - {$this->doors} doors - {$this->fuelType}";
    }
}

// Usage
$car = new Car("Toyota", "Camry", 2023, 4, "Gasoline");
echo $car->getCarDetails();
echo $car->start();

6️⃣ Abstract Classes

abstract class Shape {
    protected $color;

    public function __construct($color) {
        $this->color = $color;
    }

    // Regular method
    public function getColor() {
        return $this->color;
    }

    // Abstract methods - must be implemented in child classes
    abstract public function calculateArea();
    abstract public function draw();
}

class Circle extends Shape {
    private $radius;

    public function __construct($color, $radius) {
        parent::__construct($color);
        $this->radius = $radius;
    }

    public function calculateArea() {
        return pi() * pow($this->radius, 2);
    }

    public function draw() {
        return "Drawing {$this->color} circle with radius {$this->radius}";
    }
}

💡 OOP Best Practices

1. Follow Single Responsibility Principle: Each class has one purpose only
2. Use Inheritance Wisely: Only when there's an "is-a" relationship
3. Favor Composition over Inheritance: Use "has-a" instead of "is-a" when possible
4. Write Testable Code: Separate responsibilities
5. Use Interfaces: To ensure compatibility

Next Step

After mastering OOP, move to Design Patterns and SOLID Principles.

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