Custom E-Commerce UPI Gateway Integration

For independent e-commerce brands, custom PHP shops, and Indian dropshippers, high payment aggregator processing fees (typically 2% + 18% GST) drastically eat into profit margins. Furthermore, traditional payment gateways hold funds in rolling reserves or enforce T+2 to T+3 settlement cycles, restricting cash flow needed for immediate inventory procurement and courier COD remits.

With UPIGateway.dev, e-commerce stores can accept direct-to-bank UPI payments at 0% commission. Funds deposit immediately into the store owner's linked bank account (PhonePe, GPay, Paytm, or Bank QR), enabling same-day inventory fulfillment.

E-Commerce Checkout Flow Architecture

1. Cart Review: Customer completes shipping details and proceeds to payment.
2. Order Creation: Server calls /api/create-order passing total cart value, order reference, and customer contact details.
3. Dynamic QR & Intent Modal: The checkout page renders an embedded QR code or redirects to the clean /pay/:token screen.
4. Automated Bank Verification: As soon as the customer approves the payment, our engine validates bank records and dispatches a verified webhook POST.
5. Inventory Deduction & Order Dispatch: Your e-commerce backend locks inventory, marks the order 'Processing', and dispatches tracking information.

PHP E-Commerce Checkout Example

Here is a lightweight, dependency-free PHP script to create an order and handle the secure verification callback in any custom cart:

<?php
// cart_checkout.php — Universal PHP Cart UPI Checkout
require_once 'config.php';

$cartTotal   = 1299.00; // Calculated from cart session
$orderNumber = 'CART_' . time();
$customerEmail = filter_var($_POST['email'] ?? '', FILTER_SANITIZE_EMAIL);

// Call UPIGateway.dev /api/create-order
$payload = [
    'user_token'   => UPIGATEWAY_TOKEN,
    'amount'       => $cartTotal,
    'order_id'     => $orderNumber,
    'redirect_url' => 'https://myeshop.com/checkout/success.php?order=' . $orderNumber,
    'remark1'      => 'Cart Order #' . $orderNumber,
    'remark2'      => $customerEmail
];

$ch = curl_init('https://upigateway.dev/api/create-order');
curl_setopt_array($ch, [
    CURLOPT_POST           => true,
    CURLOPT_POSTFIELDS     => json_encode($payload),
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER     => ['Content-Type: application/json'],
    CURLOPT_TIMEOUT        => 15
]);

$response = curl_exec($ch);
curl_close($ch);
$result = json_decode($response, true);

if (!empty($result['status']) && !empty($result['result']['payment_url'])) {
    // Redirect customer to the secure payment screen
    header('Location: ' . $result['result']['payment_url']);
    exit;
} else {
    die('Failed to initialize payment: ' . htmlspecialchars($result['message'] ?? 'Unknown error'));
}

Handling Webhooks & Preventing Double Fulfillment

Ensure your webhook listener performs strict validation before updating your database:

<?php
// webhook_listener.php — Secure Webhook Callback
$rawInput = file_get_contents('php://input');
$data     = json_decode($rawInput, true);

$orderId = $data['order_id'] ?? null;
if (!$orderId) {
    http_response_code(400);
    exit('Missing order_id');
}

// 1. Verify with Gateway API
$verifyCh = curl_init('https://upigateway.dev/api/check-order-status');
curl_setopt_array($verifyCh, [
    CURLOPT_POST           => true,
    CURLOPT_POSTFIELDS     => json_encode([
        'user_token' => UPIGATEWAY_TOKEN,
        'order_id'   => $orderId
    ]),
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER     => ['Content-Type: application/json']
]);
$verifyRes = json_decode(curl_exec($verifyCh), true);
curl_close($verifyCh);

$isCompleted = ($verifyRes['status'] === true || $verifyRes['status'] === 'COMPLETED') &&
               (($verifyRes['result']['status'] ?? '') === 'COMPLETED');

if ($isCompleted) {
    // Mark order Paid in MySQL and trigger warehouse dispatch
    $stmt = $pdo->prepare("UPDATE orders SET payment_status = 'PAID', utr = ? WHERE order_number = ? AND payment_status != 'PAID'");
    $stmt->execute([$verifyRes['result']['utr'] ?? ($data['utr'] ?? ''), $orderId]);
    
    echo json_encode(['status' => 'SUCCESS']);
} else {
    http_response_code(400);
    echo json_encode(['status' => 'PENDING_OR_FAILED']);
}