An issue with Access denied for user ' @ ' localhost ' to database

$conn New mysqli ("127.0.0.1", ' abc ', ', ', db_database);

In the case of providing a user name, unexpectedly returns an error saying that the user provided by the user is empty, very peculiar problem.

Find some information that will be set to an empty user if the provided user does not exist, but the user I provide is present.

Finally found that in MySQL, I do not know when to set an empty user name of the user, any user, if any user's password is empty, then you provide a password is empty user (even if there is), will be changed to empty users.

Workaround: Remove any users from the MySQL user, empty users.

An issue with Access denied for user ' @ ' localhost ' to database