On PHPMac.com today, they have this new tutorial posted to help you, the OS X (Tiger) user to get Apache 2 and PHP 5.1.1 installed on your system.
Since Apple don't include Apache 2 with OS X yet I have felt it better to keep Apache 2 in its own directory, and to keep PHP for Apache 2, etc. confined the that directory too.
For anyone that has been wishing to switch to Apache 2 on their Mac, this is the time to do it. PHP 5 has also recently been updated to 5.1.1 and this tutorial describes in detail, the best method to both build and install these programmes on your Mac.
As usual, they give you all of the commands and information to get it all unpacked, placed in the right locations, and configured for your setup. There are also a few "frequent issues" down near the end of the tutorial to watch out for during your process...