working with remote images

It looks like my attempt to send this bounced. Which is fine, since I've now got a slightly different question. I'm working on a "network" for my site and others related to it. We want to keep track of which sites are the most popular by having everyone place on their site something to the effect of <img src="http://www.mywebsite.com/image.php?somevariables=here"> I want to then have image.php make note of which site requested it and add to their tally in the database. Then feed them the image requested. But my concern is if that image is on my server I'll be getting a lot more bandwidth. So I'm wondering if its possible to then have image.php tell the requesting server to grab their own copy of the image and load it up? I have a feeling php will grab the image from the other site's server, download it to my server and then upload it back to them. Even worse :) Thanks, Matt