A database named maintainstate is used in some of the example.  

Before reviewing the sample code, import maintainstate.sql into PHPMyAdmin.It will create a database named maintainstate. The database includes one table named users.  

The class examples are coded to be used on localhost in a Windows environment using WAMP, PHP, MySQL
$DBConnect =  mysqli_connect("localhost", "root", "");

If working on a MAC using MAMP, PHP, and MySQL use the following code:
$DBConnect =  mysqli_connect("localhost", "root", "root");

Note: maintainstate.sql has been included in more than one folder. HOwever, it only needs to be imported one time.
