When you see this error message, you properly do not config your php.ini well and so that it cannot connect to mysql server.
1. Wrong path for the mysql.sock
mysql.sock is the instance of the mysql, so first you have to find where does it place at.
You may find it at "/tmp/mysql.sock" or "/var/mysql/mysql.sock".
Go to your php.ini and make sure the value for "pdo_mysql.default_socket", "mysql.default_socket", "mysqli.default_socket" is the right path.
Then restart your web server and try again. Good Luck =]
