PHP session_start() overwrites HTTP Expires header

I am trying to set Expire header to 2 hours from access for text/html by using mod_expires like that:

<IfModule mod_expires.c>
   ExpiresActive on
   ExpiresDefault "access plus 2 hours"
   E开发者_高级运维xpiresByType text/html "access plus 2 hours"
</IfModule>

However when used with PHP:

session_start();

Expires header is being reset to:

Expires: Thu, 19 Nov 1981 08:52:00 GMT

Any ideas how to avoid that overwrite by session_start()?

OK, looks like have found an answer:

session_cache_limiter('public');
session_start();

does the trick, thanks.