What I'm doing

I'm pulling an image from the database and sending it to the browser with all the proper headers - the image displays fine. I also send an ETag header, using the SHA1 of the image's content as the tag.

The images are getting called semi regularly, so caching is a bit of an issue (won't kill the site, but nice to have).

The Problem

$_SERVER['HTTP_IF_NONE_MATCH'] is not available to me. As far as I can tell, this is because of PHP's "disobey the cache controls" life style. I can't mess with the session cache limiter, because I don't have access. But, even if I did have access, I wouldn't want to touch it: 99% of the site is under WordPress.

The Environment

• PHP 4 (don't ask)
• Apache 2.2
• WordPress
• The images live in the database (largeblog), which I can't change.

Any guidance, tip/tricks, etc. would be helpful. I don't have much room to change the environmental/structural stuff.

Cheers.