🟢 Beginner Level

1. Class & Object

class Car {
    public $brand;
    public $model;    public function showDetails() {
        echo "Brand: $this->brand, Model: $this->model";
    }
}$car1 = new Car();
$car1->brand = "Toyota";
$car1->model = "Fortuner";
$car1->showDetails();

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2. Constructor

class Student {
    public $name;
    public $age;    public function __construct($name, $age) {
        $this->name = $name;
        $this->age = $age;
    }    public function show() {
        echo "$this->name is $this->age years old";
    }
}$s = new Student("Aditya", 22);
$s->show();

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3. Calculator

class Calculator {
    public function add($a, $b) {
        return $a + $b;
    }
    public function subtract($a, $b) {
        return $a - $b;
    }
    public function multiply($a, $b) {
        return $a * $b;
    }
    public function divide($a, $b) {
        return $b != 0 ? $a / $b : "Cannot divide by zero";
    }
}$c = new Calculator();
echo $c->add(5, 3);

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🟡 Intermediate Level

4. Inheritance

class Animal {
    public function makeSound() {
        echo "Animal sound";
    }
}class Dog extends Animal {
    public function makeSound() {
        echo "Bark";
    }
}class Cat extends Animal {
    public function makeSound() {
        echo "Meow";
    }
}$d = new Dog();
$d->makeSound();

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5. Encapsulation

class BankAccount {
    private $balance = 0;    public function deposit($amount) {
        $this->balance += $amount;
    }    public function withdraw($amount) {
        if ($amount <= $this->balance) {
            $this->balance -= $amount;
        } else {
            echo "Insufficient balance";
        }
    }    public function getBalance() {
        return $this->balance;
    }
}$acc = new BankAccount();
$acc->deposit(1000);
$acc->withdraw(300);
echo $acc->getBalance();

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6. Static

class Counter {
    public static $count = 0;    public static function increment() {
        self::$count++;
    }
}Counter::increment();
Counter::increment();
echo Counter::$count;

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7. Constants

class MathConstants {
    const PI = 3.14;    public function circleArea($r) {
        return self::PI * $r * $r;
    }
}$m = new MathConstants();
echo $m->circleArea(5);

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🔵 Advanced Level

8. Abstract Class

abstract class Shape {
    abstract public function area();
}class Circle extends Shape {
    private $r;    public function __construct($r) {
        $this->r = $r;
    }    public function area() {
        return 3.14 * $this->r * $this->r;
    }
}class Rectangle extends Shape {
    private $w, $h;    public function __construct($w, $h) {
        $this->w = $w;
        $this->h = $h;
    }    public function area() {
        return $this->w * $this->h;
    }
}

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9. Interface

interface Payment {
    public function pay($amount);
}class CreditCard implements Payment {
    public function pay($amount) {
        echo "Paid $amount using Credit Card";
    }
}class PayPal implements Payment {
    public function pay($amount) {
        echo "Paid $amount using PayPal";
    }
}

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10. Polymorphism

class Circle {
    public function draw() {
        echo "Drawing Circle";
    }
}class Square {
    public function draw() {
        echo "Drawing Square";
    }
}function render($shape) {
    $shape->draw();
}render(new Circle());
render(new Square());

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11. Magic Methods

class User {
    public $name;    public function __construct($name) {
        $this->name = $name;
        echo "User Created<br>";
    }    public function __destruct() {
        echo "User Destroyed";
    }    public function __toString() {
        return "User: " . $this->name;
    }
}$u = new User("Aditya");
echo $u;

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12. File Handling

class FileManager {
    public function write($file, $data) {
        file_put_contents($file, $data);
    }    public function read($file) {
        return file_get_contents($file);
    }
}$f = new FileManager();
$f->write("test.txt", "Hello World");
echo $f->read("test.txt");

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🔴 Real-World

13. Simple Login System (Basic)

class User {
    private $username;
    private $password;    public function register($u, $p) {
        $this->username = $u;
        $this->password = password_hash($p, PASSWORD_DEFAULT);
    }    public function login($u, $p) {
        if ($this->username === $u && password_verify($p, $this->password)) {
            return "Login Success";
        }
        return "Login Failed";
    }
}$user = new User();
$user->register("admin", "1234");
echo $user->login("admin", "1234");

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14. Shopping Cart

class Product {
    public $name, $price;    public function __construct($name, $price) {
        $this->name = $name;
        $this->price = $price;
    }
}class Cart {
    private $items = [];    public function add(Product $p) {
        $this->items[] = $p;
    }    public function total() {
        $sum = 0;
        foreach ($this->items as $item) {
            $sum += $item->price;
        }
        return $sum;
    }
}$cart = new Cart();
$cart->add(new Product("Phone", 10000));
$cart->add(new Product("Laptop", 50000));
echo $cart->total();

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15. Blog System (Basic Structure)

class Post {
    public $title;    public function __construct($title) {
        $this->title = $title;
    }
}class Comment {
    public $text;    public function __construct($text) {
        $this->text = $text;
    }
}class User {
    public $name;    public function __construct($name) {
        $this->name = $name;
    }
}

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