Webhooks in PHP (Receive External Events Safely)

Webhooks are server-to-server callbacks. Example: - Stripe sends “payment_succeeded” to your endpoint - your server updates the order status ## Webhook rules 1) Always verify signature (if provider supports it) 2) Respond fast (200 OK) and process heavy work in background 3) Make webhook handlers idempotent (same event can arrive twice) ## Idempotency concept ```mermaid flowchart TD A[Webhook Event] --> B{Event ID already processed?} B -->|Yes| C[Ignore safely] B -->|No| D[Process + store event id] ``` > Next: Unit testing in PHP with PHPUnit (foundations).