Are php includes the same as http requests?

I have what I hope does not turn out as a stupid question. This is something trivial (perhaps) that I have been wondering about for a while.

For instance:
We use CSS image sprites to cut down on http requests turning what might be 8 image http requests into 1 which helps cut down on bandwidth, correct?

When we organize php code, we like to make several folders for cleanness and keeping everything modular, etc.

So, do all these php includes have the same bandwidth usage effect as an http request such as an image or css file?

Are they cached like an image or css file? Since they are server side pre-page load I am assuming they are not cached?

 

php includes are all done server side, so you don't need to worry about bandwidth.