Warning: mysqli_connect(): (HY000/1045): Access denied for user 'simple'@'127.0.0.1' (using password: YES) in /home/simple/public_html/core/db.php on line 2

Warning: mysqli_error() expects exactly 1 parameter, 0 given in /home/simple/public_html/core/db.php on line 2
I cannot connect to the database because: