Why MAMP doesn't display errors?

MAMP sets up a few different php.ini files for the server, the client etc. Check in your phpinfo() which php.ini actually is read. Looks like you're editing the wrong one.

There are two php.ini files on MAMP. You should change both php.ini files.

1. Applications/MAMP/bin/php/'php version you are using(php5.5.10)'/conf/php.ini
2. Applications/MAMP/conf/php/'php version you are using(php5.5.10)'/conf/php.ini

Then change:

display_errors = Off 

to:

display_errors = On

If you're using MAMP PRO, you've to enable Error handling (PHP) in the UI interface which should contain at least two the main options: 'Display startup errors' and set output 'To: Display'.

Display startup errors option is equivalent to display_startup_errors (in PHP) and To: Display to display_errors.

See below: