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?

Processing includes occurs entirely on the server. There are no additional http requests involved.

You can think of it as just telling PHP to find a certain file and copy its content into the currently executing script.

Wow thanks NullPointer!
I kind of thought that but was not sure. I have breaking a bunch of files for a recent wordpress theme and was starting to wonder if i was having too many.

As NullPointer "pointed" out, not really - unless you do something like this: include 'http://somedomain.com/testfile.php'; PHP can do that and in that case, it is making a request everytime the code is run. However, standard includes where you are just referencing a file system path make no http request.