I need a cache system for PHP that suport tags.
It's will be used caching a lot of queries results, from many users, and every time I will need to clear some user cache, or some module cache...
I thinked, and conclude that tagging are the best way to do that.
Like ('messages_unread_user_300','messages','user_300','unread') it easy to clearup when needed.
I've tried xcache and apc.
The memcached wiki has a solution that looks like it may fit yours:
http://code.google.com/p/memcached/wiki/NewProgrammingTricks#Namespacing
See "Deleting By Namespace"