Validate XML With Zend_Form

App_Validate_Xml.php

<?php
class App_Validate_Xml extends Zend_Validate_Abstract
{
	const ERROR_MESSAGE = 'error';
	
	public $xmlError;
	
	protected $_messageVariables = array(
		'xmlError' => 'xmlError'
	);
	
	protected $_messageTemplates = array(
		self::ERROR_MESSAGE => '%xmlError%'
	);
	
 	public function isValid($value)
	{
		libxml_use_internal_errors(true);
		
		$dom = new DOMDocument('1.0', 'utf-8');
		$dom->loadXML($value);
		
		$errors = libxml_get_errors();
		
		if(count($errors) > 0) {
			foreach($errors as $error) {
				$this->xmlError = $error->message;
				$this->_error(self::ERROR_MESSAGE);
			}
			return false;
		}
		return true;
	}
}