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: { ...