how can I save a xml on a website and reload later?

In a simple way, all I want is a way for make a web-site where the user changes a xml table(add, edit and remove), save the xml in a file and can load a xml file for substitute the current one.

The site content is based on xml information, but I need the user can save and load the xml content, and I don't know how to do it.

Can someone help me?