ClickCartPro and EuropaCart have an excellent debugger embedded in all of their functions.
The debugger is turned on by editing the file:
{private}/core/CORE/CORE.php
At the top of that file you will see:
var $debug = 0;
Change the debug mode to ‘1’ to log to a file in the {PRIVATE}/temp directory. Change to ‘2’ to log to the browser window. If you choose to log to the browser window.