Description:
------------
Actually I posted this bug to Apache, but they said this is PHP bug.

I noticed that ETag responce header from PHP script is simply ignored. If there comes a request with "If-None-Match" and the script responds with "ETag" that matches it, the server responds with "200 OK" status. When checked with static content, Apache has no problem responding with "304 Not Modified". 
There is no problem when script responds with "Last-Modified", and the server then ends up with "304 Not Modified". 

What I got from Apache bug report system:

This is a php bug. The handler (read: PHP) is responsible for calling
ap_meets_conditions at the proper place (i.e. before sending the content) or
doing the evaluation that takes place there itself.

Please address this issue to the php bug database.

Regards,
Dennis

Reproduce code:
---------------
Request:
GET /temp/etag.php HTTP/1.1
If-None-Match: "0-1234-12345678"

Responce:
HTTP/1.1 200 OK  -- should be 304 as for static content is
ETag: "0-1234-12345678"

Whereas using time-related headers:
Request:
GET /temp/etag.php HTTP/1.1
If-Modified-Since: Thu, 31 Jul 2003 19:12:11 GMT

Responce:
HTTP/1.1 304 Not Modified  -- as expected
Last-Modified: Thu, 31 Jul 2003 19:12:11 GMT

Also combining two kinds of headers is useless:
Request:
GET /temp/etag.php HTTP/1.1
If-None-Match: "0-1234-12345678"
If-Modified-Since: Thu, 31 Jul 2003 19:12:11 GMT

Responce:
HTTP/1.1 200 OK  -- Note this happens despite Last-Modified!
ETag: "0-1234-12345678"
Last-Modified: Thu, 31 Jul 2003 19:12:11 GMT