Paypal Integration

# 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

```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})

});

});

}

}).render('#paypal-button-container');

</script>

```

```python

# 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

```python

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.c