mysqli_stmt::bind_result(): Number of bind variables doesn't match number of fields in prepared statement
Solution 1:
$mysqli->prepare("SELECT username, password FROM users WHERE username = ?");
$username = $_POST['name'];
$stmt->bind_param('s' ,$username);
$stmt->execute();
$stmt->bind_result($username, $password);
Your select syntax was wrong, the correct syntax is
SELECT field1, field2, field3 FROM TABLE WHERE field1 = ? AND field2 = ?
To select more fields simply separate them by a comma and not an AND