I had this problem in the past with MAMP on a Windows machine.
Open MAMP start page and go to your current configuration of PHP (phpinfo). Check the Configuration File (php.ini) PATH.
Mine was set to C:\Windows, where of course I had no PHP.ini file.
Either change the php.ini path to C:\MAMP\conf\php5.6.8 (or your php version conf path) or just copy php.ini to c:\windows.