$resp = new \Symfony\Component\HttpFoundation\Response('test',\Symfony\Component\HttpFoundation\Response::HTTP_UNPROCESSABLE_ENTITY);
        $resp->headers->set('MyHeader','MyValue');
        $resp->send();

// headers
foreach ($this->headers->allPreserveCase() as $name => $values) {
    foreach ($values as $value) {
        header($name.': '.$value, false, $this->statusCode);
    }
}

// status
header(sprintf('HTTP/%s %s %s', $this->version, $this->statusCode, $this->statusText), true, $this->statusCode);