Classes, Objects, and Properties

A class is a blueprint; an object is an instance created from it.

class Product
{
    public string $name;
    public float $price;
    private int $stock = 0;

    public function __construct(string $name, float $price)
    {
        $this->name = $name;
        $this->price = $price;
    }

    public function restock(int $quantity): void
    {
        $this->stock += $quantity;
    }

    public function getStock(): int
    {
        return $this->stock;
    }
}

$laptop = new Product('Laptop', 999.99);
$laptop->restock(10);
echo $laptop->name;       // 'Laptop'
echo $laptop->getStock(); // 10

Visibility modifiers control access: public (accessible from anywhere), protected (accessible from the class and its subclasses), private (accessible only from within the same class).

Constructor property promotion (PHP 8.0+) removes the boilerplate of declaring properties separately:

class Product
{
    public function __construct(
        public string $name,
        public float $price,
        private int $stock = 0,
    ) {}
}

Static properties and methods belong to the class itself, not any instance: ClassName::$staticProp and ClassName::staticMethod(), useful for counters, factories, or utility methods that don't need object state.