When a payment is received, blockchain.info will notify the callback URL you specify. Please note, the callback url is limited to 255 characters in length.
transaction_hash - The payment transaction hash.
address - The destination bitcoin address (part of your xPub account).
confirmations - The number of confirmations of this transaction.
value - The value of the payment received (in satoshi, so divide by 100,000,000 to get the value in BTC).
{custom parameter} - Any parameters included in the callback URL will be passed back to the callback URL in the notification. You can use this functionality to include parameters in your callback URL like invoice_id or customer_id to track which payments are associated with which of your customers.
source:
https://blockchain.info/api/api_receive
