Payments Built for the GSM Industry

// 1. Create an Idempotent GSMXPay Invoice
$payload = [
    'public_key'     => 'pk_live_YOUR_PUBLIC_KEY',
    'order_id'       => 'DHRU-INV-90421',
    'amount'         => '50.00',
    'currency'       => 'USDT',
    'customer_email' => '[email protected]',
    'callback_url'   => 'https://your-gsm-server.com/webhook/gsmxpay',
    'success_url'    => 'https://your-gsm-server.com/orders/90421'
];

$ts  = (string)time();
$sig = hash_hmac('sha256', $ts . '.' . json_encode($payload), $apiSecret);

// Headers: X-PayGSM-Timestamp: $ts | X-PayGSM-Signature: $sig | Idempotency-Key: uuid-v4
// Response: {"status":"success","payment_id":"PGS...","payment_url":"https://.../checkout/PGS..."}

// 2. Verify Inbound GSMXPay Webhook Callback
$rawBody = file_get_contents('php://input');
$data    = json_decode($rawBody, true);

$receivedSig = $data['signature'] ?? '';
unset($data['signature']);

$expectedSig = hash_hmac('sha256', json_encode($data), $merchantSecret);
if (!hash_equals($expectedSig, $receivedSig)) {
    http_response_code(401);
    exit('Invalid signature');
}

if (($data['status'] ?? '') === 'paid') {
    // Safely credit GSM reseller wallet once per unique payment_id
    creditResellerWallet($data['order_id'], $data['payment_id'], $data['amount']);
}

// 3. GSMXPay Client Concept (WHMCS / DHRU / Custom PHP)
$intent = GSMXPay::intents()->create([
    'order_id'       => $invoiceId,
    'amount'         => $creditPackageTotal,
    'currency'       => 'USDT',
    'idempotencyKey' => 'order_' . $invoiceId,
]);

header('Location: ' . $intent->payment_url);
exit;