code: public function send()
      {
          if ($this->isSent) {
              return;
          }
          $this->trigger(self::EVENT_BEFORE_SEND);
          $this->prepare();
          $this->trigger(self::EVENT_AFTER_PREPARE);
          $this->sendHeaders();
          $this->sendContent();
          $this->trigger(self::EVENT_AFTER_SEND);
          $this->isSent = true;
      }
docs: Sends the response to the client.