Set-Cookie and Expires headers differ

Question

I'm trying to enable Expires headers for images as recommended by YSlow. I'm sure I had this working before but now when I check YSlow it says they are not being cached.

For my .htaccess, I have tried:

ExpiresActive on
ExpiresDefault A0
<FilesMatch "\.(gif|ico|jpg|png)$">
    ExpiresDefault A29030400
    Header append Cache-Control "public"
</FilesMatch>

and

ExpiresActive on
ExpiresByType image/gif "access plus 1 month"
ExpiresByType image/jpeg "access plus 1 month"
ExpiresByType image/png "access plus 1 month"
ExpiresByType image/x-icon "access plus 1 month"

http://www.seoconsultants.com/tools/headers.asp outputs the following for one of my images:

HTTP Status Code: HTTP/1.1 200 OK
Date: Mon, 05 Oct 2009 20:12:04 GMT
Server: Apache/2.0.63 (Unix) mod_ssl/2.0.63 OpenSSL/0.9.8e-fips-rhel5 mod_bwlimited/1.4 PHP/5.2.8
X-Powered-By: PHP/5.2.8
Set-Cookie: PHPSESSID=5d11f4d8aa37ceee6605786e59ff4f0f; path=/
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Set-Cookie: lastlogin=1254773024; expires=Mon, 02-Nov-2009 20:12:04 GMT
Connection: close
Content-Type: image/jpeg

The Set-Cookie part looks correct but the Expires header is not. How do I set Expires correctly and why do they differ? I have double checked that mod_expires and mod_headers are enabled.

Answer 1

From the Set-Cookie header, it looks like this is part of a php session. php automatically disables caching after a session_start().

You can modify this behavior by changing session.cache_limiter in your php.ini. See the PHP manual page for the various settings.

Alternatively, you could try using "set" instead of "append" to override the headers in your .htaccess.