Developer guide

The License class, its constants and statuses, and how Pro takes over from Lite.

Coding standards and the release checklist.

What the plugin deliberately does not do, and why.

AJAX and admin endpoints, and the checkout script’s data and behaviour.

Sandbox, tunnels for webhooks, logging, simulating webhooks and mocking the API.

Order, subscription and customer meta, options and transients.

Filters and actions the plugin provides, and the EDD hooks it uses.

Locks, fresh reads, markers, the renewal state machine and the refund ledger.

How refunds travel from EDD to Paddle and from Paddle to EDD.

The Recurring_Gateway overrides, status mapping, and pause and resume.

How a cart becomes Paddle lines, and the one-time, subscription, Billing and Classic checkout flows.

The endpoint, signature checks and how each Billing event and Classic alert is handled.

Design principles, files, boot sequence, drivers and API clients.

Where settings live, every key, and the helpers to read them.

Architecture, payment and webhook flows, stored data, safety mechanisms, hooks and local testing.