Manipulation of soap headers

I've googled far and wide for hints on how to add custom soap headers  
using ext/Soap to no avail.

I've seen various posting on the serialization of the XML to objects  
(eg the underscore property), but i've seen no way to set attributes  
on headers explicitly. for example:

	<ns2:Framework version="2.0"/>

perhaps i am missing something very basic... and FWIW, I have to do  
the same for the server's response....

any advice or pointers greatly appreciated.

=peterd