I may have been making that up re: redis, honestly. It's guilty by association in my mind, but I've used redis in PHP a lot without any first hand problems.
But Memcached, certainly (and even doubly so for the `Memcache` extension that ill-informed developers install instead of the better `Memcached`), and the others listed, either are slower/etc or just don't exist.
Fair enough, I'm sure you're right with some of the other lesser used libraries e.g. Riak. It's probably fair to say it takes PHP longer in general to get a good client library than say Python. Not sure about Ruby.
But Memcached, certainly (and even doubly so for the `Memcache` extension that ill-informed developers install instead of the better `Memcached`), and the others listed, either are slower/etc or just don't exist.