> For the complete documentation index, see [llms.txt](https://docs.chamilo.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.chamilo.org/developer-guide/developer-guide/backend.md).

# Backend

The Chamilo 3.0 backend is built on Symfony 7.4 with Doctrine ORM and API Platform.

* [**Symfony Architecture**](/developer-guide/developer-guide/backend/symfony-architecture.md) — Bundles, services, and the overall backend structure
* [**Entities and Doctrine**](/developer-guide/developer-guide/backend/entities-and-doctrine.md) — The Doctrine entity classes and how they relate
* [**Resource System**](/developer-guide/developer-guide/backend/resource-system.md) — The ResourceNode/ResourceFile abstraction (key architectural concept)
* [**Controllers**](/developer-guide/developer-guide/backend/controllers.md) — Controller organization and routing patterns
* [**Events and Listeners**](/developer-guide/developer-guide/backend/events-and-listeners.md) — How Chamilo uses the Symfony event system
* [**Settings System**](/developer-guide/developer-guide/backend/settings-system.md) — The settings schemas in `src/CoreBundle/Settings/` and how platform configuration works