PHP User Login System Help

So after searching the web for weeks and weeks for a good tutorial, something registered in my head, "Maybe GitHub has one that someone else has already built and tested!"

Sure enough I found one here https://github.com/TazChris/phpUserLoginSystem and it looks great. I was trying to implement it into my site and I get this issue

Warning: mysqli::mysqli(): (HY000/2005): Unknown MySQL server host 'login' (0) in /Applications/MAMP/htdocs/controller/classes/AuthDB.class.php on line 8

Warning: mysqli::prepare(): Couldn't fetch mysqli in /Applications/MAMP/htdocs/controller/classes/AuthDB.class.php on line 21

Fatal error: Call to a member function bind_param() on a non-object in /Applications/MAMP/htdocs/controller/classes/AuthDB.class.php on line 27

I think the issue is coming from the config.php file that is being required_once at the top of the AuthDB.class.php file. Right now I'm using MAMP. I have a database named login with the tables already set up with file included with the download. My code for the config.php file is set up like this

<?php
  //Database information
  define("DB_SERVER", "localhost");
  define("DB_USER", "root");
  define("DB_PASS", "root");
  define("DB_NAME", "localhost");
  //Database table information 
  define("USER_TABLE", "tbUsers");
  define("LOGGED_IN_TABLE", "tbLoggedInUsers");
  //Fully Qualified Domain Name
  define("SITE_HTTP", "http://localhost:8888");
  //Return email address
  define("FROM_EMAIL", "");
?>

Any ideas on what I might be doing wrong?