User::getInstance

static function getInstance($userId = null): self
{
	global $USER;

	$userId = (int)$userId;
	if ($userId <= 0 && is_object($USER) && $USER->GetID() > 0)
	{
		$userId = (int)$USER->GetID();
	}

	if (!isset(self::$instance[$userId]))
	{
		self::$instance[$userId] = new self($userId);
	}

	return self::$instance[$userId];
}