Andrei Zmievski has posted about updates that have been made to the memcached extension for PHP:

The first project the I've been working on since joining Digg has seen the light of day. It's a new PHP extension for interfacing with memcache servers and it is based on the libmemcached library, which is becoming the standard client library for this task. [...] There is another memcache PECL extension, but this one offloads the intricacies of communicating with memcache onto libmemcached and instead concentrates on exposing a sensible API and some cool features like asynchronous requests and read-through caching callbacks.

You can find out more about the extension on its PECL project page and more about the memcached library from the project's website.