public function send()
    {
        if (!static::isSent()) {
            static::call('send', $this);
            foreach ($this->headers as $header => $value) {
                $this->setHttpHeader($header, $value);
            }
            http_response_code($this->status);
            echo $this->body;
            static::$sent = true;
            return true;
        }
        return false;
    }