Using PHP to write XML

Is it possible to write to an XML file with PHP?

I have a simple Flash/XML slideshow-esque presentation that uses images+audio.

I want to hand it over to a client but I think managing the XML is too advanced for them.

I’m thinking I might need to hand over an HTML form with some PHP to allow them to upload assets and add/delete slides. If I could make it in Flash, that would be even better. I’m thinking that if I do it in Flash, I can set an interval to keep reloading the XML in so the client can see their edits as they create a presentation.

I’ve used PHP to write to .txt files for simple hit counters etc. that I’ve used in Flash, but this is a bit over my head.

Anyone?