Here's the hook you want:
'PageRenderingHash'...
Thanks very much, Brion. Do you have an example of using this hook when you want multiple
user options not to be cached? The examples on
http://www.mediawiki.org/wiki/Category:PageRenderingHash_extensions are really minimal and
involve cryptic things like "!" characters when the docs say to use a
"hash", e.g.,
function ImageFilterHash( $hash )
...
$hash .= '!' . ( $wgUser->getOption( 'displayfiltered' ) ?
'1' : '' );
Thanks,
DanB