UI Callback

* The Callback is sent to a URL that is passed in X-REDIRECT-URL header along with request. * The value of X-REDIRECT-MODE header should be POST to get UI callback.

Form Post Response Payload

Parameter Name	Description
`code` Enum	See list of codes.
`merchantId` String	merchantId
`transactionId` String	Unique Transaction ID
`amount` Long	Transaction amount in paise
`providerReferenceId` String	PhonePe ReferenceId.
`param1` String	Optional Parameter, to be used later
`param2` String	Optional Parameter, to be used later
`param3` String	Optional Parameter, to be used later
`param4` String	Optional Parameter, to be used later
`param5` String	Optional Parameter, to be used later
`param6` String	Optional Parameter, to be used later
`param7` String	Optional Parameter, to be used later
`param8` String	Optional Parameter, to be used later
`param9` String	Optional Parameter, to be used later
`param10` String	Optional Parameter, to be used later
`param11` String	Optional Parameter, to be used later
`param12` String	Optional Parameter, to be used later
`param13` String	Optional Parameter, to be used later
`param14` String	Optional Parameter, to be used later
`param15` String	Optional Parameter, to be used later
`param16` String	Optional Parameter, to be used later
`param17` String	Optional Parameter, to be used later
`param18` String	Optional Parameter, to be used later
`param19` String	Optional Parameter, to be used later
`param20` String	Optional Parameter, to be used later
`checksum` String	The checksum for this entire request

How is checksum computed for a Form POST?

The server itself will generate the checksum, by doing a SHA256(code + merchantId + transactionId + amount + providerReferenceId + param1 + param2 +...... + param20 + saltKey).
The salt we would use will be appended with ### to the checksum value in the checksum attribute. Merchants upon receiving this payload, will look at the salt_index in the checksum attribute after ### delimiter and use the appropriate salt_index to be able to calculate checksum at their end for the said payload. If it doesn't match, then they will need to abort the request.
Salts are already pre-shared with the merchant when they are onboarded.
If value of any parameter is null, it will not be included in calculation of checksum.

Transaction Status Response Codes

Code	Description
`TRANSACTION_NOT_FOUND`	Payment not initiated inside PhonePe
`BAD_REQUEST`	Invalid request
`AUTHORIZATION_FAILED`	X-VERIFY header is incorrect
`INTERNAL_SERVER_ERROR`	Something went wrong. Merchant needs to call Check Transaction Status to verify the transaction status.
`PAYMENT_SUCCESS`	Payment is successful
`PAYMENT_ERROR`	Payment failed
`PAYMENT_PENDING`	Payment is pending. It does not indicate failed payment. Merchant needs to call Check Transaction Status to verify the transaction status.
`PAYMENT_DECLINED`	Payment declined by user
`PAYMENT_CANCELLED`	Payment cancelled by the merchant using Cancel API