---
title: "Classes"
manual: "TYPO3 Explained"
version: "11.5"
permalink: "https://docs.typo3.org/permalink/t3coreapi:extension-classes@11.5"
source: "ExtensionArchitecture/FileStructure/Classes/Index.rst"
rendered: "2026-10-21T15:30:00+00:00"
---

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# `Classes` {#extension-classes}

Contains all PHP classes. One class per file. Should have sub folders like
`Controller/`, `Domain/`, `Service/` or `View/`.
For more details on class file namings and PHP namespaces, see chapter
[namespaces](https://docs.typo3.org/permalink/t3coreapi:namespaces@11.5).

-   **Classes/Controller**

    Contains MVC Controller classes.

-   **Classes/Domain/Model**

    Contains MVC Domain model classes.

-   **Classes/Domain/Repository**

    Contains data repository classes.

-   **Classes/ViewHelpers**

    Helper classes used in (Fluid) views.