I've been working with AJAX for about a year now and something that I have not figured out yet is how to deal with xml that is not well formed. Typically, I will pass the xmlhttprequest object's responseXML to a function and if the passed xml is not well formed, a fatal error occurs and my script won't work. I have tried using try...catch to catch the error but that doesn't work. Can anyone shed some light how to test if the returned XML is well formed?

In what circumstances would that happen?

--

Joe (Microsoft MVP - XML)

I generate most of the XML via PHP. When the PHP script fails either because of fatal errors, or whatever else is causing the problem, the returned XML is not valid.

Well I think the PHP code should be changed to return an XML formatted error message if something goes wrong. Alternatively you will have to use the responseText property of the XmlHTTPRequest and first see if it's well-formed by trying to load it into an XML DOM. If it's not then use the text somehow. The first method seems easier and more resilient. If you are using SOAP style messages then this is what the SOAP fault was created for.

--

Joe (Microsoft MVP - XML)