Accept UPI payments with three API calls

<?php
$ch = curl_init('https://zappay-beta.vercel.app/api/developer/create-order');
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode([
    'zap_api'      => 'YOUR_ZAPAPI_KEY',
    'amount'       => 100,
    'title'        => 'Order #123',
    'redirect_url' => 'https://yourstore.com/payment-return.php'
]));

$response = curl_exec($ch);
curl_close($ch);

$result = json_decode($response, true);

if ($result['success']) {
    // Send the customer to complete payment
    header('Location: ' . $result['data']['payment_url']);
    exit;
} else {
    // Handle error — see API Reference for all possible messages
    echo 'Could not start payment: ' . $result['message'];
}

<?php
// $_GET['zp_order'] and $_GET['zp_result'] are appended by ZapPay automatically.
// IMPORTANT: zp_result in the query string must NEVER be trusted alone —
// it can be spoofed. Always confirm via order-status server-side.

$orderId = $_GET['zp_order'] ?? null;

if (!$orderId) {
    die('Missing order id.');
}

$ch = curl_init("https://zappay-beta.vercel.app/api/developer/order-status/{$orderId}");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'X-ZapAPI-Key: YOUR_ZAPAPI_KEY'
]);

$response = curl_exec($ch);
curl_close($ch);

$result = json_decode($response, true);

if ($result['success'] && $result['data']['status'] === 'success') {
    // Verified server-side — safe to fulfill the order now
    echo 'Payment confirmed for order ' . $result['data']['order_id'];
} elseif ($result['success'] && $result['data']['status'] === 'pending') {
    echo 'Payment still pending — check again shortly.';
} else {
    echo 'Payment failed or order not found.';
}

OkHttpClient client = new OkHttpClient();
String ZAP_API_KEY = "YOUR_ZAPAPI_KEY";
String BASE_URL = "https://zappay-beta.vercel.app";

// 1. Create the order
public void createOrder(double amount, String title, OrderCallback callback) {
    JSONObject body = new JSONObject();
    try {
        body.put("zap_api", ZAP_API_KEY);
        body.put("amount", amount);
        body.put("title", title);
        body.put("useEmbedded", true);
    } catch (JSONException e) {
        callback.onError(e.getMessage());
        return;
    }

    RequestBody requestBody = RequestBody.create(
        body.toString(), MediaType.parse("application/json"));

    Request request = new Request.Builder()
        .url(BASE_URL + "/api/developer/create-order")
        .post(requestBody)
        .build();

    client.newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(Call call, IOException e) {
            callback.onError(e.getMessage());
        }

        @Override
        public void onResponse(Call call, Response response) throws IOException {
            try {
                JSONObject json = new JSONObject(response.body().string());
                if (json.getBoolean("success")) {
                    JSONObject data = json.getJSONObject("data");
                    String orderId = data.getString("order_id");
                    String paymentUrl = data.getString("payment_url");

                    // 2. Open payment_url in a Chrome Custom Tab
                    openCustomTab(paymentUrl);

                    // 3. Start polling for the result
                    pollOrderStatus(orderId, callback);
                } else {
                    callback.onError(json.getString("message"));
                }
            } catch (JSONException e) {
                callback.onError(e.getMessage());
            }
        }
    });
}

void openCustomTab(String url) {
    CustomTabsIntent intent = new CustomTabsIntent.Builder().build();
    intent.launchUrl(context, Uri.parse(url));
}

// Poll order-status every ~2.5s until it resolves
Handler handler = new Handler(Looper.getMainLooper());

public void pollOrderStatus(String orderId, OrderCallback callback) {
    Request request = new Request.Builder()
        .url(BASE_URL + "/api/developer/order-status/" + orderId)
        .header("X-ZapAPI-Key", ZAP_API_KEY)
        .get()
        .build();

    client.newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(Call call, IOException e) {
            callback.onError(e.getMessage());
        }

        @Override
        public void onResponse(Call call, Response response) throws IOException {
            try {
                JSONObject json = new JSONObject(response.body().string());
                if (json.getBoolean("success")) {
                    String status = json.getJSONObject("data").getString("status");

                    if (status.equals("success")) {
                        callback.onSuccess(json.getJSONObject("data"));
                    } else if (status.equals("failed")) {
                        callback.onFailed(json.getJSONObject("data"));
                    } else {
                        // still "pending" — poll again in 2.5s
                        handler.postDelayed(() ->
                            pollOrderStatus(orderId, callback), 2500);
                    }
                } else {
                    callback.onError(json.getString("message"));
                }
            } catch (JSONException e) {
                callback.onError(e.getMessage());
            }
        }
    });
}

public interface OrderCallback {
    void onSuccess(JSONObject data);
    void onFailed(JSONObject data);
    void onError(String message);
}