Payment Integration (Stripe or PayPal)

Example Code

```php
<?php

require_once 'vendor/autoload.php'; // Ensure Composer autoloader is included

// Set your secret key. Remember to switch to your live secret key in production.
// You can find your keys here: https://dashboard.stripe.com/apikeys
\Stripe\Stripe::setApiKey('sk_test_YOUR_STRIPE_SECRET_KEY');

header('Content-Type: application/json');

$input = file_get_contents('php://input');
$data = json_decode($input, true);

if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($data['paymentMethodId']) && isset($data['amount'])) {
    $paymentMethodId = $data['paymentMethodId'];
    $amountInCents = $data['amount']; // Amount in cents, e.g., $10.00 is 1000
    $currency = 'usd'; // Or 'eur', 'gbp', etc.

    try {
        // Create a PaymentIntent with the specified amount and currency
        $paymentIntent = \Stripe\PaymentIntent::create([
            'amount' => $amountInCents,
            'currency' => $currency,
            'payment_method' => $paymentMethodId,
            'confirmation_method' => 'manual', // Manual confirmation for better control
            'confirm' => true, // Confirm the PaymentIntent immediately
            'return_url' => 'http://localhost/payment_success.php', // URL for 3D Secure redirects (if needed)
            // 'description' => 'Example charge for user X',
            // 'metadata' => ['order_id' => '12345'],
        ]);

        // Handle the payment intent status
        if ($paymentIntent->status == 'succeeded') {
            echo json_encode([
                'success' => true,
                'message' => 'Payment succeeded!',
                'paymentIntent' => $paymentIntent->id
            ]);
        } elseif ($paymentIntent->status == 'requires_action' && $paymentIntent->next_action->type == 'use_stripe_sdk') {
            // This case handles 3D Secure authentication or other actions required by the customer.
            // You would typically send client_secret back to the client to complete the payment on the frontend.
            echo json_encode([
                'requires_action' => true,
                'paymentIntentClientSecret' => $paymentIntent->client_secret
            ]);
        } else {
            // Other statuses like 'requires_payment_method', 'requires_confirmation', etc.
            echo json_encode([
                'success' => false,
                'message' => 'Payment failed or requires further action: ' . $paymentIntent->status,
                'paymentIntent' => $paymentIntent->id,
                'status' => $paymentIntent->status
            ]);
        }

    } catch (\Stripe\Exception\CardException $e) {
        // A decline or other error occurred
        http_response_code(400);
        echo json_encode([
            'success' => false,
            'message' => $e->getError()->message
        ]);
    } catch (\Stripe\Exception\RateLimitException $e) {
        http_response_code(429);
        echo json_encode(['success' => false, 'message' => 'Too many requests, please try again.']);
    } catch (\Stripe\Exception\InvalidRequestException $e) {
        http_response_code(400);
        echo json_encode(['success' => false, 'message' => 'Invalid request: ' . $e->getMessage()]);
    } catch (\Stripe\Exception\AuthenticationException $e) {
        http_response_code(401);
        echo json_encode(['success' => false, 'message' => 'Authentication with Stripe failed.']);
    } catch (\Stripe\Exception\ApiConnectionException $e) {
        http_response_code(500);
        echo json_encode(['success' => false, 'message' => 'Network communication with Stripe failed.']);
    } catch (\Stripe\Exception\ApiErrorException $e) {
        // Display a very generic error to the user, and log the error for yourself.
        http_response_code(500);
        echo json_encode(['success' => false, 'message' => 'An unexpected error occurred: ' . $e->getMessage()]);
    } catch (Exception $e) {
        http_response_code(500);
        echo json_encode(['success' => false, 'message' => 'Internal server error: ' . $e->getMessage()]);
    }

} else {
    http_response_code(400);
    echo json_encode(['success' => false, 'message' => 'Invalid request method or missing data.']);
}

// --- Client-side (HTML & JavaScript) example (for context, not part of the PHP code block itself) ---
/*
<script src="https://js.stripe.com/v3/"></script>
<form id="payment-form">
    <div id="card-element"><!-- Stripe Elements will create input fields here --></div>
    <button id="submit-button">Pay Now</button>
    <div id="payment-message" role="alert"></div>
</form>
<script>
    const stripe = Stripe('pk_test_YOUR_STRIPE_PUBLISHABLE_KEY'); // Replace with your publishable key
    const elements = stripe.elements();
    const cardElement = elements.create('card');
    cardElement.mount('#card-element');

    const form = document.getElementById('payment-form');
    const submitButton = document.getElementById('submit-button');
    const messageContainer = document.getElementById('payment-message');

    form.addEventListener('submit', async (event) => {
        event.preventDefault();
        submitButton.disabled = true;

        const { paymentMethod, error } = await stripe.createPaymentMethod({
            type: 'card',
            card: cardElement,
        });

        if (error) {
            messageContainer.textContent = error.message;
            submitButton.disabled = false;
        } else {
            // Send the paymentMethod.id to your server
            const response = await fetch('/your-backend-payment-endpoint.php', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({
                    paymentMethodId: paymentMethod.id,
                    amount: 1000 // Example amount in cents (e.g., $10.00)
                }),
            });

            const paymentResult = await response.json();

            if (paymentResult.success) {
                messageContainer.textContent = paymentResult.message;
                // Redirect or show success message
            } else if (paymentResult.requires_action) {
                // Handle 3D Secure or other required actions
                const { error: confirmError } = await stripe.confirmCardPayment(
                    paymentResult.paymentIntentClientSecret
                );

                if (confirmError) {
                    messageContainer.textContent = confirmError.message;
                } else {
                    messageContainer.textContent = 'Payment confirmed! You can now check your Stripe dashboard.';
                    // Payment confirmed after action, now handle success
                }
            } else {
                messageContainer.textContent = paymentResult.message;
            }
            submitButton.disabled = false;
        }
    });
</script>
*/

?>
```