Warning: mysqli_connect(): (HY000/2002): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) in /home/kahwinma/public_html/include/config.php on line 19

Warning: mysqli_connect(): (HY000/2002): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) in /home/kahwinma/public_html/include/config.php on line 21

Warning: mysqli_error() expects exactly 1 parameter, 0 given in /home/kahwinma/public_html/include/config.php on line 21
I cannot connect to the database because: