xml with php

Please can you guide me, I want to use php to update the following xml with the values the user fills in. for example add value="" in the "input type text" line and add checked to the Radio button line. Is there any functions in php that can be used to step through a xml and just update the form object lines(e.g. Text, Radio, Check...) <?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="app.xsl"?> <?cocoon-process type="xslt"?> <Form> <Text LABEL="NAME" SIZE="24" NAME="Name"/> <Radio LABEL="10" NAME="AGE" VALUE="10"/> <Radio LABEL="20" NAME="AGE" VALUE="20"/> <Check LABEL="stamps" NAME="hobby" VALUE="stamps"/> </Form> Any guidance would be greatly appreciated, Thank, Steve __________________________________________________ Do You Yahoo!? Yahoo! Auctions - buy the things you want at great prices http://auctions.yahoo.com/