calling php from javascript?

Is this possible? I'm converting a heavy javascript based site to a dynamic php but my problem is that the navigation sytem is very graphic orinentated and is hard coded with large and complex javascript. (multiple js files) So instead of writing all the javascript through php I would like to call where necessary small snipits of php (which build the menu dynamically) and then revert back to the original javascript when necessary. is this possible to call a separte php include in a js file? thanks.