code: private function toXml($elementName, $rootElement = false)
      {
          return sprintf(
              '%s<%s%s%s>%s</%s>',
              $rootElement ? "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" : '',
              $elementName,
              $this->attributesToXml(),
              array_key_exists(get_class($this), self::$xmlNamespaces) ? sprintf(' %s', self::$xmlNamespaces[get_class($this)]) : '',
              $this->propertiesToXml(),
              $elementName
          );
      }
docs: Converts the object to a XML string.
  
  @param string $elementName The XML element that the object's properties will be a children of.
  @param bool $rootElement Indicates if the XML will be the root element.
  
  @return string The XML.