static function get_subdomain() { if (is_null(self::$subdomain)) { if (defined('ROUTE_DOMAIN_NAME') === FALSE) { define('ROUTE_DOMAIN_NAME', $_SERVER['HTTP_HOST']); } self::$subdomain = preg_replace('/^(?:([^\\.]+)\\.)?' . ROUTE_DOMAIN_NAME . '$/', '\\1', $_SERVER['HTTP_HOST']); } return self::$subdomain; }