paypal-integration

# PayPal Integration

Master PayPal payment integration including Express Checkout, IPN handling, recurring billing, and refund workflows.

## When to Use This Skill

- Integrating PayPal as a payment option
- Implementing express checkout flows
- Setting up recurring billing with PayPal
- Processing refunds and payment disputes
- Handling PayPal webhooks (IPN)
- Supporting international payments
- Implementing PayPal subscriptions

## Core Concepts

### 1. Payment Products
**PayPal Checkout**
- One-time payments
- Express checkout experience
- Guest and PayPal account payments

**PayPal Subscriptions**
- Recurring billing
- Subscription plans
- Automatic renewals

**PayPal Payouts**
- Send money to multiple recipients
- Marketplace and platform payments

### 2. Integration Methods
**Client-Side (JavaScript SDK)**
- Smart Payment Buttons
- Hosted payment flow
- Minimal backend code

**Server-Side (REST API)**
- Full control over payment flow
- Custom checkout UI
- Advanced features

### 3. IPN (Instant Payment Notification)
- Webhook-like payment notifications
- Asynchronous payment updates
- Verification required

## Quick Start

```javascript
// Frontend - PayPal Smart Buttons
<div id="paypal-button-container"></div>

<script src="https://www.paypal.com/sdk/js?client-id=YOUR_CLIENT_ID&currency=USD"></script>
<script>
  paypal.Buttons({
    createOrder: function(data, actions) {
      return actions.order.create({
        purchase_units: [{
          amount: {
            value: '25.00'
          }
        }]
      });
    },
    onApprove: function(data, actions) {
      return actions.order.capture().then(function(details) {
        // Payment successful
        console.log('Transaction completed by ' + details.payer.name.given_name);

        // Send to backend for verification
        fetch('/api/paypal/capture', {
          method: 'POST',
          headers: {'Content-Type': 'application/json'},
          body: JSON.stringify({orderID: data.orderID})
        }