I downloaded the most recent version of XAMPP (v.1.7.7) and decided start a database. When I opened phpMyAdmin, it alerts me there is a new version of phpMyAdmin available.
In new versions note that you have to change your code to like this:
mysqli_connect($mysql_hostname, $mysql_username, $mysql_password, $mysql_dbname);
And for more look to this: Fatal error: Uncaught Error: Call to undefined function mysql_connect()