PHP not locating mcrypt while using MAMP
I don't think MAMP relies on the php package installed in Terminal (or in OS X for that matter). MAMP uses it's own php version located at /Applications/MAMP/bin/php/php5.5.3

The modules are in the folder I noted above in a subfolder called /modules. You would have to manually get mcrypt in the modules folder for MAMP to work with mcrypt.