Create a checkout

cURL

# Step 1: create the checkout. Put the request in a file, so the JSON is exactly what you wrote, for example
#   {"reference":"ORD-10021","amount":1500,"paymentMethod":"qr","paymentType":"onetime","returnUrl":"https://shop.example.com/orders/ORD-10021"}
# The answer carries checkoutUrl: send the customer there.
antpay_create_checkout() {   # antpay_create_checkout FILE_WITH_JSON_BODY
  antpay_call POST /api/v1/checkouts "$(cat "$1")"
}

Part of antpay.sh, the complete tested file

Node.js

// Step 1: create the checkout on your server, store the checkoutId, redirect the customer.
async function createCheckout(order) {
  if (!REFERENCE.test(order.id)) throw new Error('reference: use letters, digits, ".", "_" and "-" only (1 to 120 characters)');
  const { http: status, json } = await call('POST', '/api/v1/checkouts', {
    reference: order.id,                 // your order id, unique per API key
    amount: order.total,                 // whole rupees, minimum 300
    paymentMethod: 'qr',
    paymentType: 'onetime',
    returnUrl: `https://shop.example.com/orders/${encodeURIComponent(order.id)}`,
  });
  if (status === 200 && json && json.success) {
    return { checkoutId: json.checkoutId, checkoutUrl: json.checkoutUrl, expiresAt: json.expiresAt };
  }
  // 4xx: nothing was created (a duplicate reference already exists: look it up).
  // 5xx or no answer: the checkout may exist. Ask by reference before you retry.
  const error = new Error(`checkout not created (HTTP ${status})`);
  error.status = status;
  error.body = json;
  throw error;
}

Part of antpay.js, the complete tested file

PHP

// Step 1: create the checkout on your server, store the checkoutId, redirect the customer.
function antpay_create_checkout(string $orderId, int $total): array {
    if (!preg_match(ANTPAY_REFERENCE, $orderId)) throw new InvalidArgumentException('reference: use letters, digits, ".", "_" and "-" only (1 to 120 characters)');
    [$status, $data] = antpay_call('POST', '/api/v1/checkouts', [
        'reference' => $orderId,            // your order id, unique per API key
        'amount' => $total,                 // whole rupees, minimum 300
        'paymentMethod' => 'qr',
        'paymentType' => 'onetime',
        'returnUrl' => 'https://shop.example.com/orders/' . rawurlencode($orderId),
    ]);
    if ($status === 200 && is_array($data) && !empty($data['success'])) {
        return ['checkoutId' => $data['checkoutId'], 'checkoutUrl' => $data['checkoutUrl'], 'expiresAt' => $data['expiresAt']];
    }
    // 4xx: nothing was created (a duplicate reference already exists: look it up).
    // 5xx or no answer: the checkout may exist. Ask by reference before you retry.
    throw new RuntimeException("checkout not created (HTTP $status): " . json_encode($data));
}

Part of antpay.php, the complete tested file

Python

# Step 1: create the checkout on your server, store the checkoutId, redirect the customer.
def create_checkout(order_id, total):
    if not REFERENCE.match(order_id):
        raise ValueError('reference: use letters, digits, ".", "_" and "-" only (1 to 120 characters)')
    status, data = call("POST", "/api/v1/checkouts", {
        "reference": order_id,              # your order id, unique per API key
        "amount": total,                    # whole rupees, minimum 300
        "paymentMethod": "qr",
        "paymentType": "onetime",
        "returnUrl": "https://shop.example.com/orders/" + urllib.parse.quote(order_id, safe=""),
    })
    if status == 200 and data and data.get("success"):
        return {"checkoutId": data["checkoutId"], "checkoutUrl": data["checkoutUrl"], "expiresAt": data["expiresAt"]}
    # 4xx: nothing was created (a duplicate reference already exists: look it up).
    # 5xx or no answer: the checkout may exist. Ask by reference before you retry.
    raise RuntimeError(f"checkout not created (HTTP {status}): {data}")

Part of antpay.py, the complete tested file