A php include is like taking another file and literally putting it in another file.
There is no way that I know of to hide them nor do I think you should try to hide them.
The "hiding" of css you are talking about is putting it in a separate .css file.
This is not done to hide it, any user could go into the source get the link and type it in. This is done to
one: make your code look neater.
Two: have it easy on yourself, for multiple pages (only have to type it once).
Remember the PHP is never sent to the client it goes through the Php engine running on the server translated into plain html and THEN sent to the client.
Don't know anything about webspell sorry.
Hope some of this helped