For simplicity check drush status with verbose and debug parameters:

drush -vd status 

If you're using different profile, don't forget to include it as -l http://foo.

If you still have a problem, it's an issue with bootstrapping your Drupal.

First check your SQL connection if it's working:

drush sql-cli 

If it does not, check your db credentials in your Drupal settings file.

If it does, there is a problem with SQL connection through the socket.

So in MAMP you've to do:

1. Check value of socket in my.cnf (menu: File/Edit Template), it's usually set as:

   socket = /Applications/MAMP/tmp/mysql/mysql.sock 

2. Double check if your MySQL can find this file:

   $ mysql_config --socket /Applications/MAMP/tmp/mysql/mysql.sock 

3. Double check if your PHP has the right mysql.sock set-up:

   $ php -i | grep mysql.default_socket 

4. Link the socket into your /tmp and see if that helps:

   sudo ln -s /Applications/MAMP/tmp/mysql /var/mysql 

5. Test the socket file:

   mysql --socket=/var/mysql/mysql.sock 

6. Still the problem? Add the following setting into your $databases:

   $databases['default']['default'] = array( // ... 'unix_socket' => '/var/mysql/mysql.sock', 

Troubleshooting

• Try: drush sqlq "SELECT @@version_comment LIMIT 1"
• Try: drush ev "Database::getConnection('default', 'default');"
• Try: mysql --socket=$(php -r 'echo ini_get("mysql.default_socket");')
• Check permissions on Unix socket: stat $(mysql_config --socket)
• Debug: on OS X with sudo dtruss -fn mysqld, on Linux with strace

• Debug with XDebug:

  • echo '<?php xdebug_start_trace("/tmp/foo.log");' > init.php
  • drush -c init.php ev 'Database::getConnection("default", "default");'
  • or set xdebug.show_exception_trace=1 in your xdebug.ini

• Check MySQL settings:

  • echo '<?php phpinfo();' > init.php
  • drush -c init.php ev 'Database::getConnection("default", "default");' | grep mysql

• Run: php -r "new PDO('mysql:host=localhost;port=3306;charset=utf8;dbname=dbname', 'root', 'root');"

• Try to rebuilt your registry