code: public function send($data = null)
      {
          $statusCode = null;
  
          if ($data instanceof self) {
              return $data->send();
          }
  
          if (is_string($data)) {
              $this->setBody($data);
          }
  
          if (is_array($data) && isset($data[0])) {
              $this->setBody($data[0]);
          }
  
          if (is_array($data) && isset($data[1]) && is_numeric($data[1])) {
              $statusCode = $data[1];
          }
  
          $this->setStatusCode($statusCode);
  
          if (!headers_sent()) {
              $this->sendHeaders();
          }
  
          echo $this->getBody();
          return $this;
      }
docs: Send response supporting several ways of receiving response $data.
  
  @param mixed $data to use as optional base for creating response.
  
  @return self