Currently, .htaccess disables ExpiresActive for index.php. This should really apply to all .php files. The mod_expires stuff is intended for static files. PHP scripts should set their caching headers explicitly.
The current behaviour is a problem e.g. in this situation:
If you access update.php while your database is unavailable, you will get a WSOD, and the response will contain the header
Cache-Control: max-age=1209600. Now, if you were accessing the server through e.g. an office proxy server, the proxy would cache that page, and you have to hit CTRL+F5 to force the proxy to fetch the page again (some proxies don't allow this).
This patch is inspired by Davy Van Den Bremt's suggested fix for.
FAILED: [[SimpleTest]]: [MySQL] Unable to apply patch mod_expires-D6-1_0.patch. View
Passed: 12056 passes, 0 fails, 0 exceptions View
FAILED: [[SimpleTest]]: [MySQL] Unable to apply patch mod_expires-1.patch. View