Not using cached version

Hi, I have some images stored in a database (only file name and other relevant information, rest stored in file system). I use the following html to access them: <img src='image.php?imageid=123' /> At some pages I have the same image, so that tag will be seen on multiple places on the same page. So what I am curious is why all of the different images are loaded separately, instead of just recognizing that they are the same and use a cache version? This is the code that do all the work: Header ("Content-type: $image_type"); readfile("files/$image"); I am a little bit lost here; kick me in the right direction if you can :) /Peter www.lauri.se - my personal blog www.dwsasia.com - the company I work for