a merchant could use a single allPay merchant account for multiple shops (it is especially true for the test accounts)
a merchant could change (e.g., reset) his Magento store order numeration scheme so the new Magento order numbers will overlap with the previous allPay payment identifiers.
If allPay encounters a payment identifier (the MerchantTradeNo parameter value) which has been already used for another payment, it fails with the message: «訂單編號重覆,建立失敗(100002)» (it can be translated as «failed to make a payment because the order number is already in use»):
It is needed because:
If allPay encounters a payment identifier (the
MerchantTradeNo
parameter value) which has been already used for another payment, it fails with the message: «訂單編號重覆,建立失敗(100002)» (it can be translated as «failed to make a payment because the order number is already in use»):