payment-gateway-integration

Secure payment processing integrates official SDKs for Stripe, PayPal, and Square to handle payment intents, subscriptions, and refunds. Use sandbox mode to test, validate webhook signatures to verify events, and enable PCI compliance by never storing raw card data. Deploy to production only after sandbox validation.

Webhook handling requires validating signatures from your payment gateway to ensure authenticity, processing events idempotently to handle retries safely, and never logging sensitive payment data. Stripe, PayPal, and Square all provide signature verification methods in their SDKs to confirm webhook origin.

Recurring subscriptions use payment gateway APIs to create subscription objects with billing cycles, while refunds capture payment IDs and request reversal through the same gateway. Both require idempotent request handling to prevent duplicate charges and robust error handling for declined or failed transactions.

Multiple gateways can coexist in a single checkout by routing customer selections to the appropriate SDK—Stripe for cards, PayPal for accounts, Square for in-person or alternative methods. Each maintains separate payment intents and webhook endpoints, requiring unified reconciliation logic.

PCI compliance mandates never storing or logging raw card numbers, using official payment SDKs that handle sensitive data, validating webhooks to confirm transaction authenticity, and implementing error handling without exposing card details. This approach avoids direct card data handling, shifting compliance responsibility to certified gateways.

Transaction reconciliation matches payment gateway records—Stripe charges, PayPal transactions, Square payments—against your order database using unique payment IDs and timestamps. Webhook event handling tracks status changes and captures refunds or disputes, ensuring all gateway records sync with your storefront ledger.