> For the complete documentation index, see [llms.txt](https://wiki.relictum.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.relictum.pro/developing/relictum-finance/callback.md).

# Callback

Cryptobank will send a request to the URL you specified when the status of the order you have created changes to successful or canceled.

Response sample

```json
{
    "currency":  "USDT-TRX",   
    "id":  "374",   
    "status":  "SUCCESS",
    "sum":  "185",   
    "sum_currency":  "186",   
    "verify_hash":  "SECRET_HASH"     
}
```

* id — order ID in the cryptobank you saved after your purchase request.
* verify\_hash — a message signature that allows you to verify that the request came from a cryptobank.

Please note that the USDR amount \<sum> and the currency amount \<sum\_currency> may differ from the values set when the transaction was created (for example, if the end user transferred an amount different from the set one).

Make sure your code handles the value of each return parameter correctly.

Possible values of the status field:

* SUCCESS — transaction paid
* CANCEL — transaction cancelled

Verify\_hash transaction (example on PHP):

```php
$data = $_POST;
unset($data['verify_hash']);
ksort($data);
$dataString = serialize($data);
$checkKey = hash_hmac('sha1', $dataString, CALLBACK_API_KEY);
    
if ($checkKey != $_POST[''verify_hash'']) {
  return false;
}
```

Expected response if the event was successfully processed:

```json
{
   "success":  true
}
```

In case of a different answer, the cryptobank will continue sending the request until a correct answer is received, or until the limit set in the API settings is reached.


---

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