Editing xml using flash,php,asp

i know that to update or write to a xml file u need to use php or asp with that.
i use the xml connector to display my xml inflash.
4 component
lesson number == combo box
lesson title ==text area
description ==text area
save button == btn

if i to edit the description and lesson title. can anyone show me a simple php or asp code.
or can show me but actionscript to put in the save button