My Windows installation has the following lines in httpd.conf (adjsut path appropriately):
LoadModule php5_module "c:/wamp/bin/php/php5.2.9-2/php5apache2_2.dll"
In the mime_module section:
AddType application/x-httpd-php .php
PS: I just realized the first line specifying a .dll is probably very Windoze specific, so you'll need to figure out which Mac file to point it to.
PPS: Hopefully the PHP install manual will clarify this for you in the Mac OSX section.