Since you are using PHP5, how about a Curl replacement for direct URL file gets?
This would allow a site that has URL file restrictions to still use the script using a Curl alternative.
Then you could use simplexml_load_string instead of simplexml_load_file to parse the same data using a simple switch in the script.
I’ve run into problems a number of times recently where the ISP blocked file URL access but Curl worked fine.
BTW I don’t write for PHP4 any longer.