Building an XML Parser Class

Hi, I am trying to create a Class that will parse an XML document. It all works fine as individual functions but I cant get it to work as a class. For example, when I do the following in my class: xml_set_element_handler($this->xml_parser, '$this->startElement', "$this->endElement"); xml_set_character_data_handler($this->xml_parser, "$this->valueHandler"); I get an error message: Warning: xml_parse(): Unable to call handler $this->startElement() in c:\program files\apache group\php\My_includes\Class.xmlTranslator.php on line 90 Now I presume this is because I am trying to call methods of my class. Does anyone know a good way around this? Thanks.