$this->_helper->layout()->disableLayout();
		$this->_helper->viewRenderer->setNoRender(true);
		        
		$xml = new DOMDocument('1.0', 'utf-8');
		$xml->appendChild($xml->createElement('video', 'link'));
		$output = $xml->saveXML();
	
		Zend_Controller_Action_HelperBroker::getStaticHelper('viewRenderer')->setNoRender(true);
		Zend_Layout::getMvcInstance()->disableLayout();
	
		$this->_response->setHeader('Content-Type', 'text/xml; charset=utf-8')
			->setBody($output);

Zend output XML

php, xml

PHP