ZF2 How to return XML response

simple_response.php

<?php
$rawXml = '<foo><bar>Baz</bar></foo>';
 
$response = new \Zend\Http\Response();
// Instead of header("Content-type: text/xml; charset=utf-8") use:
$response->getHeaders()->addHeaderLine('Content-Type', 'text/xml; charset=utf-8'); 
$response->setContent($rawXml);
return $response;

strategy_responce.php

<?php
namespace SomeNamespace\Controller;
 
use Zend\View\Model\JsonModel;
use Zend\View\Model\FeedModel;
use AP_XmlStrategy\View\Model\XmlModel;
 
class SomeController extends AbstractActionController
{
    protected $acceptCriteria = array(
        'Zend\View\Model\JsonModel' => array(
            'application/json',
        ),
        'Zend\View\Model\FeedModel' => array(
            'application/rss+xml',
        ),
        'AP_XmlStrategy\View\Model\XmlModel' => array(
            'application/xml',
        ),
    );
 
    public function apiAction()
    {
        $viewModel = $this->acceptableViewModelSelector($this->acceptCriteria);
 
        if ($viewModel instanceof JsonModel) {
            return new JsonModel(array(
                'response' => 'foo',
                )
            );
        }
 
        if ($viewModel instanceof FeedModel) {
            return new FeedModel(array(
                'response' => 'foo',
                )
            );
        }
 
        if ($viewModel instanceof XmlModel){
            return new XmlModel(array(
                'response' => 'foo',
                )
            );
        }
    }
}

xmlwriter_response.php

<?php
 
namespace Chart\Controller;
 
use Zend\Mvc\Controller\AbstractActionController;
use Zend\View\Model\ViewModel;
 
use XMLWriter;
 
class IndexController extends AbstractActionController
{
    public function graphAction()
    {
    	$rawXml = '<foo><bar>Baz</bar></foo>';
 
    	$writer= new XmlWriter();
        $writer->openMemory();
        $writer->startDocument('1.0', 'UTF-8');
        $writer->writeRaw($rawXml);
        $writer->endDocument();
 
        $response = $this->getResponse();
    	$response->getHeaders()->addHeaders(array('Content-type' => 'text/xml'));
    	$response->setContent($writer->outputMemory());
	return $response;
    }
}

Please read http://blog.webdevilopers.net/how-to-render-xml-response-in-zend-framework-2/ for details.