Classes & Objects

<?php
class Car {
    // Properties (data)
    public string $brand;
    public string $color;
    public int $year;

    // Method (behavior)
    public function describe(): string {
        return "{$this->year} {$this->brand} in {$this->color}";
    }

    public function honk(): void {
        echo "Beep beep!";
    }
}
?>

<?php
// Create objects from the class
$car1 = new Car();
$car1->brand = "Toyota";
$car1->color = "red";
$car1->year  = 2022;

$car2 = new Car();
$car2->brand = "Honda";
$car2->color = "blue";
$car2->year  = 2023;

echo $car1->describe();  // 2022 Toyota in red
echo $car2->describe();  // 2023 Honda in blue
$car1->honk();           // Beep beep!
?>

<?php
class BankAccount {
    public string $owner;
    private float $balance;  // hidden from outside

    public function deposit(float $amount): void {
        $this->balance += $amount;
    }

    public function getBalance(): float {
        return $this->balance;  // controlled access
    }
}

$account = new BankAccount();
$account->owner = "John";
$account->deposit(1000);
echo $account->getBalance();  // 1000

// $account->balance = 99999;  // Error! balance is private
?>

<?php
class Counter {
    public static int $count = 0;

    public static function increment(): void {
        self::$count++;
    }
}

Counter::increment();
Counter::increment();
echo Counter::$count;  // 2 — shared across all instances
?>