I am unable to send you an image or sample of the actual error, but here is my best explanation of what I experienced...
I copy and pasted the code you sent next to the other server behaviors at the top of my php page. I saved the file and uploaded the file to my hosting server. Since I received the code from you directly, I did not upload any other files from the eCart subdirectory.
I ran the checkout process agains and I was directed to a blank screen, as if the page was unable to connect to a database or the server behaviors were all out of wack. I proceeded back to DW and noticed that the shipping_failure page was not reading the code correctly. It had an error pertaining to the A_Cart_Coupons_PHP.php file...it could not find it. Also, there was an error for the WA_Cart_Coupons_USPS_FullResponse file...it could not find this file either.
I had used your online solution providing assistance in creating the server bindings to allow the page to spit back the error issues before. This process created a file in my eCart subdirectory which I had to upload. With the code you provided, there appeared to be no other file to upload.
Did I miss something?