The response to that AJAX request is just raw XML data.
showIndexPhone() is retrieving the data and setting the variable
xmlDoc to it, but it's not doing anything else with it. It's doesn't actually show it anywhere, despite the function name.
Anyway, you can use
file_get_contents() in PHP to download the XML data, and then use one of its several XML parsers to deconstruct it. There's a whole chapter in the Programming PHP book explaining how to process XML.