code: public static function start () {
          if(!self::$started) {
              // Если содержи
              if(!empty($_COOKIE[self::$cookieName]) and !ctype_alnum($_COOKIE[self::$cookieName])) {
                  unset($_COOKIE[self::$cookieName]);
              }
              session_set_cookie_params (self::$lifetime, '/');
              session_name (self::$cookieName);
              if(session_id() == '') {
                  session_start();
              }
              self::$started = true;
          }
      }
docs: Start session