Sam Holman has written up a new post on the Label Media blog today about installing Sphinx and PECL/sphinx on a Mac OS X system. No sample code is provided, but this will definitely help with the setup.
I've got a fairly vanilla install of Snow Leopard (10.6) and use the default installations of PHP, MySQL, Apache, et al. Installing the Sphinx open source search engine and the PECL extension wasn't too much of a pain, but would have been easier had i had the following notes to hand.
His first try was with Macports, but dependency issues shot that down quickly. Instead he opted for the more conventional path of: download the binaries of Sphinx and using the "pecl" command line too to install the PECL module. All that's left is adding the line to load the share object (sphinx.so) into the php.ini's config. You can find out more about the PECL sphinx package here