PayPal Integration

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

Do not use this skill when

• The task is unrelated to paypal integration
• You need a different domain or tool outside this scope

Instructions

• Clarify goals, constraints, and required inputs.
• Apply relevant best practices and validate outcomes.
• Provide actionable steps and verification.
• If detailed examples are required, open resources/implementation-playbook.md.

Use this skill when

• 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

// 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})
        });
      });
    }
  }).render('#paypal-button-container');
</script>

# Backend - Verify and capture order
from paypalrestsdk import Payment
import paypalrestsdk

paypalrestsdk.configure({
    "mode": "sandbox",  # or "live"
    "client_id": "YOUR_CLIENT_ID",
    "client_secret": "YOUR_CLIENT_SECRET"
})

def capture_paypal_order(order_id):
    """Capture a PayPal order."""
    payment = Payment.find(order_id)

    if payment.execute({"payer_id": payment.payer.payer_info.payer_id}):
        # Payment successful
        return {
            'status': 'success',
            'transaction_id': payment.id,
            'amount': payment.transactions[0].amount.total
        }
    else:
        # Payment failed
        return {
            'status': 'failed',
            'error': payment.error
        }

Express Checkout Implementation

Server-Side Order Creation

import requests
import json

class PayPalClient:
    def __init__(self, client_id, client_secret, mode='sandbox'):
        self.client_id = client_id
        self.client_secret = client_secret
        self.base_url = 'https://api-m.sandbox.paypal.com' if mode == 'sandbox' else 'https://api-m.paypal.com'
        self.access_token = self.get_access_token()

    def get_access_token(self):
        """Get OAuth access token."""
        url = f"{self.base_url}/v1/oauth2/token"
        headers = {"Accept": "application/json", "Accept-Language": "en_US"}

        response = requests.post(
            url,
            headers=headers,
            data={"grant_type": "client_credentials"},
            auth=(self.client_id, self.client_secret)
        )

        return response.json()['access_token']

    def create_order(self, amount, currency='USD'):
        """Create a PayPal order."""
        url = f"{self.base_url}/v2/checkout/orders"
        headers = {
            "Content-Type": "application/json",
            "Authorization": f"Bearer {self.access_token}"
        }

        payload = {
            "intent": "CAPTURE",
            "purchase_units": [{
                "amount": {
                    "currency_code": currency,
                    "value": str(amount)
                }
            }]
        }

        response = requests.post(url, headers=headers, json=payload)
        return response.json()

    def capture_order(self, order_id):
        """Capture payment for an order."""
        url = f"{self.base_url}/v2/checkout/orders/{order_id}