A question regarding bandwidth optimization and PHP

[sp0om]

I've been trying to optimize my site as much as possible to keep things running fast and to reduce bandwidth, but I think I need to clear up a few misconceptions I might have.

I have a header.php file where I hold all of the validation functions I use for the rest of the site. It weighs about 8kb. But, when I load a page, and save it to my desktop, the page will weigh a mere 1.5 kb.

Does that mean that the entire header.php file is not loaded? Does bandwidth only account for what is echo-ed to the browser?

[Mittineague]

The weight of the scripts will (maybe) affect server load, but bandwidth is only what is transferred in response to the request. For example, if you have script that queries a large database it will slow down the response to the request, but once the server proccesses the script then the download speed is affected by the output weight.

[Dan Grossman]

Does bandwidth only account for what is echo-ed to the browser?

Yes, as that is the only data transferred over the network from your server to the viewer.