In his latest blog post Raphael Stolt has a new guide to getting the Redis extension installed on your Mac OS X PHP setup. Redis is a key-value based storage tool.
Two out of [the list of libraries] caught my particular attention: Rediska due to it's impressive Zend Framework integration and phpredis as it's a native PHP extension written in C and therefore supposed to be blazingly faster than vanilla PHP client libraries. The following blog post will show how to install and configure the aforementioned, native PHP extension on a Mac OS X system.
You'll need to have the redis server already installed (via MacPorts or some other method) but with that and the necessary libraries in place installing the extension is a simple "git clone" away. He even includes the location of a gist (code snippet) to help you test it out.