Quote Originally Posted by peejay View Post
Seems that when modules Gift Certificates and Discount Coupons are uninstalled definitions MODULE_ORDER_TOTAL_GV_STATUS and MODULE_ORDER_TOTAL_COUPON_STATUS no longer exist.
This is correct. You should always check

if (defined('MODULE_ORDER_TOTAL_GV_STATUS')) { ...

if (defined('MODULE_ORDER_TOTAL_COUPON_STATUS')) { ...

before using these values.

In PHP 5.6, it was ok to skip checking them, but not with PHP 7+! You will see the core code in Zen Cart 1.5.7 always checks these values before using them.