On PHPBuilder.com there's a new tutorial posted about combining PHP and Ajax to move large XML data around via a web interface.

A simple way to transfer XML documents onto a server is to use an Ajax-driven Web interface to upload the files. However, this approach won't work for huge XML files because Ajax doesn't support uploading of files that large. In this article you will learn an innovative solution for transferring huge XML documents on the server via a Web interface using Ajax and the GET method.

Their method takes the XML and puts it in a string then breaks it up into chunks to make it easier to transport. These chunks are then sent via an Ajax request and pushed into an XML file. Full code is included for the tool and a few screenshots of their example in action.