it won't be a php-parameter. Seen as the script isn't executed when the server decides it is the same as the cached version. So only if it deems not to be, then it runs the script, and when it does that, the script doesn't need to know anything about modified-since, because that checks has long since been passed.
Really? It's not until the script is executed that the acutal image is accessed. Until, it's only refered to as a picture id, and int-value.
Your suggestion was to use If-Modified-Since. How and where should I do a check for it?
Best regards,
Anders