I’ve solved this, here is solution for all anyone who trys this example and has problem to get it to work.
Since you declare $wpdb as global, and since $wpdb is something that belongs to wordpress and is not part of php, you cant expect it to show up in process.php file if you do not include necessary file.
make sure you include this file like this:
require_once(“../../../wp-config.php”);
..// is used 3 times to get up from the folder where plugin is located. inside wp-config is declaration of $wpdb so then it becomes available to you in your php file…
btw thanks for the above example, I was looking into getting into developing more complex wordpress plugins and this example was perfect to get me to understand how to do it 🙂
If anyone has any more wisewords to share, plz do so
