How to return different responses from a controller

gistfile1.txt

// if the response is XML:
$response = new \Symfony\Component\HttpFoundation\Response();
$response->setContent($xml);
return $response;

// if the response is a twig template:
$template = new \SimpleSAML\XHTML\Template('whatever.twig');
$template->data = ['foo' => 'bar'];
return $template;

// finally, if the response is an old PHP template:
$template = new \SimpleSAML\XHTML\Template('whatever.tpl.php');
$template->data = ['foo' => 'bar'];
return new \Symfony\Component\HttpFoundation\StreamedResponse([$template, 'show']);