No, I'm sorry. Actually I haven't really checked out the AJAX feature in Construct 2. But as I'm a freelance web developer I've used AJAX an PHP together in many website project.
EDIT: I just noticed that the AJAX feature in Construct 2 seem to be focused only for retrieving content and not passing variables. So I might have been wrong in what I told you earlier.
But the best idea is to wait and see if someone else answers I think. I just began using Construct 2 so I haven't really got very big knowledge about the plugins available and such.