Is it "application/x-www-form-urlencoded", "multipart/form-data", "application/xml", "text/xml" or something else? And more importantly, how do I know when to use which?
This is a very old article which says to use "multipart/form-data" and that "application/x-www-form-urlencoded" is bad. Is that still valid advice? http://skew.org/xml/misc/xml_vs_http/#post
I'm not really using a framework - I want to hand-code this as much as possible.
Cheers!
It depends how you are encoding the data. You could use any of those (under the right circumstances).
If you are serving up XML as the message body without doing any other encoding on it, then you probably want application/xml.
The article has an example and mentions (with some almost decade old examples) that this is problematic if the server side processor doesn't support it.
If you are writing said processor, then you just have to make sure that you write it so that it does.