I have recently got a mac an am not used to developing on a mac at all.
I have MAMP Pro 1.9.6.1. I did a locate on php.ini and got this:
php.ini
I only have the non-pro version of MAMP but just because it loads it doesn't mean the PHP file is being found/without errors.
I renamed my php.ini files and MAMP still started but Apache returned several errors.
What are you trying to change in your php.ini file?