I had a heck of a time hunting down the location of php.ini on my Mac.  I needed to set the PHP error reporting setting to ‘true’ for my local installation.  Though I much prefer the file system organization of the Mac to Windows, I don’t know it nearly as well.  After some digging, I finally found the file.  On top of locating it, I had to set the permissions so that I could make the necessary change to the file.  Here are the steps:

1)  Find PHP5.  It’s a pain in the axe.  It’s located at /usr/local/php5/lib.
2)  Access the parent folder in the finder by typing “/usr/local/php5″ in the dialog at “Go->Go to folder…” menu item.
3)  Right click on “lib” and choose “Get Info”.
4)  Under “Ownership and Permission”, click on the lock icon.
5)  Change the permission so that you now have permission to write to the file.  You’ll have to put in your admin password a cupla times.
6)  Navigate to the “lib” menu now and find the “php.ini” file.  Double click on it and choose “TextEdit” as the application of choice (make it the default app too).
7)  Make the necessary changes and…done.