Login Page connecting to external database

When users connect to the login in page, I want users to use their username and password from an external database which is already set up instead of the current wp database. I have tried both the External Database Authentication Reloaded plugin and the External DB Connect plugin, but they do not seem to work or crash my site. What other options do I have? I have read we could tr…

$my_wpdb = new WPDB( ‘remote_user’, ‘remote_password’, ‘remote_db’, ‘remote_server’);

Will this work and how? What is the best thing I could do and how would I do this? What pages to put the coding syntax?

Duplicate: https://wordpress.org/support/topic/adding-another-database-using-wpdb-and-using-the-newdb-for-login-page?replies=1 ?