Singleton与PHP5中的工厂模式相结合

class Singleton {
    private static $instance;

    private function __construct() {}

    public static function getInstance() {
        if (null === self::$instance) {
            self::$instance = new Singleton();
        }

        return self::$instance;
    }
}

class Factory {
    public static function create($className) {
        $reflection = new ReflectionClass($className);
        return $reflection->newInstanceArgs();
    }
}

class SingletonFactory extends Singleton {
    public static function create($className) {
        return Factory::create($className);
    }
}