XML handlers in classes

I have a class that receives an XML response from a HTTP request and I am trying to parse the XML after receiving it. The problem I'm having is the error when trying to use xml set handlers, such as 'xml_set_element_handler'. It seems the class is having trouble seeing the handler functions. For instance, if I set this: xml_set_element_handler($xml_parser, 'startElement','endElement'); Then I receive the error 'Unable to call handler startElement()', I tried to put $this-> in front of the names of the functions, but same thing. Can someone show me how to use these handlers in a class? -- Robert