Common::getInstance

static function getInstance($userId, $groupId = 0, $id = null)
{
	$groupId = (int)$groupId;

	if (!$id)
	{
		$id = self::getDefaultId($groupId);
	}

	if (is_null(static::$instance) || !array_key_exists($id, static::$instance))
	{
		static::$instance[$id] = new static($id, $userId, $groupId);
	}

	return static::$instance[$id];
}