One API and one checkout for every way people pay in Bangladesh

const { Paynex } = require('./paynex');            // /docs/sdk/paynex-node.zip
const px = new Paynex({ baseUrl: 'https://paynex.xyz', keyId: process.env.PAYNEX_KEY_ID, secret: process.env.PAYNEX_SECRET });

const p = await px.createPayment({ amount: '1500.00', merchant_ref: 'INV-1042',
  return_url: 'https://shop.example/thanks', cancel_url: 'https://shop.example/cart' }, 'INV-1042-1500.00');
res.redirect(p.checkout_url);

// webhook (Express): raw body is required for the signature
app.post('/paynex/webhook', express.raw({ type: () => true }), Paynex.webhookHandler(WEBHOOK_SECRET, async (ev) => {
  if (ev.event !== 'payment.paid') return;
  const full = await px.getPayment(ev.data.id);
  if (full.status === 'paid') await markOrderPaid(full.merchant_ref, full.id);
}));

require 'Paynex.php';                                  // /docs/sdk/paynex-php.zip
$px = new Paynex('https://paynex.xyz', getenv('PAYNEX_KEY_ID'), getenv('PAYNEX_SECRET'));

$p = $px->createPayment([
    'amount' => '1500.00', 'merchant_ref' => 'INV-1042',
    'return_url' => 'https://shop.example/invoice/1042', 'cancel_url' => 'https://shop.example/invoice/1042',
], 'INV-1042-1500.00');
header('Location: ' . $p['checkout_url']);

// webhook.php
$ev = Paynex::verifyWebhook(getenv('PAYNEX_WEBHOOK_SECRET'), $_SERVER['HTTP_X_PG_SIGNATURE'] ?? null, file_get_contents('php://input'));
if ($ev['event'] === 'payment.paid' && $px->getPayment($ev['data']['id'])['status'] === 'paid') markInvoicePaid($ev['data']['id']);

c := paynex.New("https://paynex.xyz", os.Getenv("PAYNEX_KEY_ID"), os.Getenv("PAYNEX_SECRET")) // /docs/sdk/paynex-go.zip

p, err := c.CreatePayment(ctx, paynex.CreatePaymentParams{
    Amount: "1500.00", MerchantRef: "INV-1042",
    ReturnURL: "https://shop.example/thanks", CancelURL: "https://shop.example/cart",
}, "INV-1042-1500.00")
http.Redirect(w, r, p.CheckoutURL, http.StatusSeeOther)

http.Handle("/paynex/webhook", paynex.WebhookHandler(webhookSecret, func(ctx context.Context, ev *paynex.Event) error {
    if ev.Event != "payment.paid" { return nil }
    d, _ := ev.Payment()
    full, err := c.GetPayment(ctx, d.ID)
    if err == nil && full.Paid() { markOrderPaid(full.MerchantRef, full.ID) }
    return err
}))

final px = Paynex(baseUrl: 'https://paynex.xyz', keyId: env['PAYNEX_KEY_ID']!, secret: env['PAYNEX_SECRET']!); // /docs/sdk/paynex-dart.zip

final p = await px.createPayment(
  amount: '1500.00', merchantRef: 'INV-1042',
  returnUrl: 'myapp://paynex/return', cancelUrl: 'myapp://paynex/cancel',   // Flutter deep links
  idempotencyKey: 'INV-1042-1500.00');
// hand p.checkoutUrl to the app → launchUrl(..., mode: LaunchMode.inAppBrowserView)

final ev = Paynex.verifyWebhook(webhookSecret, headers['x-pg-signature'], rawBody);
if (ev.event == 'payment.paid' && (await px.getPayment(ev.data['id'])).paid) await markOrderPaid(ev.data['id']);