How to: Know your mysql and php is connect properly

How to know your mysql and php is connect properly. From my experience I like to share this knowledge.

1) Install the php and mysql in Linux properly with common configuration.
2) Create user and set the password in your database.
2) Create a php file like testdb.php and follow this code. Save it and transfer this file to your webroot. For examples on redhat base is /var/www/htdocs/html or Suse /srv/www/html.
3) Open your browser and type such as http://localhost/testdb.php

If success, the result will show you like Connecting... Using training2