Payment callback (Payment notification) will be sent to merchant's callback_url when order status is changed to pending confirming, paid, invalid, canceled, refunded or expired.

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API Callback Documentation
About common callback functionality please read in API Callbacks section.

CoinGate callback sends data below:

Name	Value
`id`	CoinGate order (invoice) ID.
`order_id`	Custom order ID of the merchant. Should be used to identify order or invoice number.
`status`	CoinGate payment status.
`price_amount`	The price set by the merchant; for example, 499.95.
`price_currency`	The currency code which defines the currency in which the merchant's goods/services are priced; for example, USD, CHF, BTC (see supported currencies).
`receive_currency`	The currency code which defines the currency in which the merchant's settlements will be paid. Currency conversions are done by CoinGate automatically. For example: EUR, USD, BTC, USDT, etc.
`receive_amount`	The amount which will be credited to the merchant when the invoice is paid. It is calculated by taking the `price` amount (converted to currency units set in `receive_currency`) and subtracting CoinGate processing fee from it.
`pay_amount`	The amount of cryptocurrency (defined by `pay_currency`) paid by the shopper.
`pay_currency`	The cryptocurrency in which the payment was made; for example, BTC, LTC, ETH.
`underpaid_amount`	The amount of cryptocurrency (defined by `pay_currency`) underpaid by the shopper; for example, if `pay_amount => 0.123`, `pay_currency => BTC`, and the shopper paid 0.12 BTC, then `underpaid_amount => 0.003`. Changes in `underpaid_amount` will not trigger additional callbacks, but when order information is retrieved using GET or LIST, latest value will be shown.
`overpaid_amount`	The amount of cryptocurrency (defined by `pay_currency`) overpaid by the shopper; for example, if `pay_amount => 0.123`, `pay_currency => BTC`, and the shopper paid 0.15 BTC, then `overpaid_amount => 0.027`. Changes in `overpaid_amount` will not trigger additional callbacks, but when order information is retrieved using GET or LIST, latest value will be shown.
`is_refundable`	Possible values: true, false. Indicates whether or not the shopper can request a refund on the invoice. Changes in `is_refundable` will not trigger additional callbacks, but when order information is retrieved using GET or LIST, latest value will be shown.
`created_at`	Invoice creation time.
`token`	Your custom token (or generated by CoinGate) to validate payment callback.
`fees`	Array of fees for Paid/Refunded/Partially refunded order
`paid_at`	Time when the invoice was fully paid. Only included when the status is paid, refunded, or partially_refunded.

Fields pay_currency, pay_amount, expire_at, payment_address are only sent when the customer chooses the currency with which he is going to pay for the invoice.

Content-Type: application/x-www-form-urlencoded

// print_r($_POST)

Array
(
    [id] => 343
    [order_id] => 14037
    [status] => paid
    [price_amount] => 1050.99
    [price_currency] => USD
    [receive_amount] => 926.73
    [receive_currency] => EUR
    [pay_amount] => 4.81849315
    [pay_currency] => BTC
    [created_at] => 2014-11-03T13:07:28+00:00
		[token] => ff7a7343-93bf-42b7-b82c-b38687081a4e
		[fees] => Array // only applies to paid/refunded/partially refunded order, otherwise empty Fee array
        (
            [0] => Array
                (
                    [type] => processing_fee
                    [amount] => 1.0
                    [currency] => Array
                        (
                            [id] => 2
                            [symbol] => EUR
                        )
                )
        )
)