How can update just php from 5.3.1 to 5.3.2 or more

[ballamp]

Hi, thanks a lot for your job,
I'm mac user and I need to install the moodl CMS that requires php 5.3.2 or hight.
I tried to install Mac OS X 1.8.1-beta1 (I have Kernel to 64 bit: yes) but I get an error that stops me the computer and I have to restart the os system.
Anybody can help me?
thanks a lot