hehe, you need the memcache module for php as well.
memcached = the daemon
memcache = the client (shapes in multiple ways. f.e. perl or php modules)
yum install memcached
is just the daemon
memcache is very neat btw. we have 2 of them as well, it's perfect for us, since we have like 50 webservers loadbalanced, so people keep theire sessions even when switching from server.