Here's a nifty tool that was posted to the ranchero.com weblog. It provides an attractive and easy to navigate front-end to the PHP documentation. Very handy for writing code when you're off the net.
The PHP Function Index for Mac OS X"is a simple browser to quickly look up any PHP function. Its search offers realtime-filtering of the function list and its AppleScript interface lets you look up functions easily from within your favorite editor (like BBEdit or any other scriptable app)."