abstract class Factory {
    abstract function getProduct();
}
class FirstFactory extends Factory {
    public function getProduct() {
        return new FirstProduct();
    }
}

abstract class Product {
};
class FirstProduct extends Product {
}

$factory = new FirstFactory();
$firstProduct = $factory->getProduct();
$factory = new SecondFactory();
$secondProduct = $factory->getProduct();

$firstProduct = new FirstProduct();
$secondProduct = new SecondProduct();