Payum is a framework-agnostic PHP payment processing library that unifies dozens of payment providers (PayPal, Stripe, Klarna, Authorize.Net, Be2Bill, Payex, Sofort, Offline, and others) behind a common API. The code reveals a dual architecture in transition: the mature 1.x action/request/reply model coexists with a newer 2.x command/handler/context model that returns typed result objects and executes through a middleware pipeline. Core capabilities include gateway factories, registry and container abstractions, token-based security URLs, pluggable storage backends (Doctrine ORM, MongoDB ODM, filesystem, Laminas), Twig template rendering, PSR-7/14/18 support, event dispatching, and currency/money handling. It is a library meant to be embedded inside Symfony, Laravel, or plain PHP applications, not a standalone service. The architecture is genuinely well-engineered: the middleware pipeline, handler map, token factory, and storage abstractions are cleanly separated and heavily unit-tested. However, the codebase is mid-migration between 1.x and 2.x APIs, with many deprecated legacy adapters and bridge classes still present. This dual-path design increases complexity and can confuse new users, but the core abstractions remain sound and reusable. The repository is a monorepo with per-gateway subpackages, extensive PHPUnit coverage, CI workflows, static analysis, and release automation. Technical drift is moderate: gateway integrations using old SOAP/XML-RPC SDKs and deprecated Symfony/Httplug bridges are aging, while the core 2.x architecture is actively maintained.
Liberapay is a production web application for recurrent monetary donations, operating as a non-profit platform. It allows donors to set up weekly, monthly, or yearly contributions to creators, teams, and organizations. The architecture is a monolithic Python web application built on the custom Aspen/Pando framework (a fork of Aspen), using PostgreSQL for persistence, Jinja2 for server-side rendering, and a mix of Stripe and PayPal for payment processing. Key entry points include the homepage (`www/index.html.spt`), user profile pages (`www/%username/index.html.spt`), donation management (`www/%username/giving/`), payment flows (`www/%username/giving/pay/stripe/%payin_id.spt`), and admin dashboards (`www/admin/`). Data flows involve user authentication via sessions and OAuth, tip creation and scheduling, payin execution through Stripe/PayPal, weekly payday settlement, and email notifications. External dependencies include Stripe, PayPal, Amazon SES (email), Sentry (error tracking), S3 (file storage), and multiple OAuth providers (GitHub, Twitter, Mastodon, etc.). The codebase is well-structured with reusable modules for payment prospect calculation, encryption, content security policy, currency handling, and OAuth abstraction, though it carries technical debt from a custom framework and aging dependencies.