我正在使用 PayPal IPN 在我的网站上处理付款。我希望用户能够输入折扣代码和传递给 PayPal 并计算的值（金额或百分比）。
我一直在网上寻找，但似乎只能找到以下内容：
Use discount_amount_cart to charge a single discount amount for the entire cart.
Use discount_amount_x to set a discount amount associated with item x
Use discount_rate_cart to charge a single discount percentage for the entire cart.
discount_rate_cart - Applies to entire cart however, this variable will only work with the "Upload" Method. Not the standard Add to Cart variables.
在我的请求字符串中测试了这些之后：
...&discount_amount_cart=10&...
PayPal 似乎不承认这个折扣。这在 PayPal IPN 中是否真的存在？
感谢您的帮助！