you have added the cart display manager to the WA_eCart\My_eCart1_PHP.php
you should not be editing that file, you should not add eCart functionality like the display manager to that file.
that file is to define your cart settings that are used by the pages in our site that you add eCart functionality to.
you will need to delete that file and recreate the eCart object for your site.
then create a new blank php page and add the cart display manager to that blank [page.