The /src directory

Is where all our namespaced code lives. This is where we develop the future backend of the Yoast SEO plugin. The code in here adheres to the following characteristics:

• Uses PHP 7.4 as its minimum PHP version.
• Uses namespaces.
• Uses dependency injection via Symphony Dependency Injection container.
• Is organized in concepts, creating a clearer separation of concerns.
• Is better isolated from WordPress and other dependencies and therefore easy to test.

Directory structure

The directory structure splits the code up into different concepts. Here's a global overview:

src
├── actions             REST actions contain the business logic which is executed on routes.
├── builders            Builders create Indexables from legacy post metadata
├── commands            Yoast WP-CLI commands.
├── conditionals        Conditionals determine whether an Integration should load.
├── config              Config objects for our tooling.
├── context             Context for our presenters. @todo these are in fact presentations, refactor.
├── deprecated          Contains all deprecated code, mostly non-namespaced.
├── exceptions          Custom Exception objects.
├── generators          Generators generate metadata pieces.
│    └── schema         Schema piece generators.
├── helpers             Helpers are simple utility services which can be used across our code.
│    └── schema         Schema helpers.
├── initializers        Initializers bootstrap the Yoast plugin / ORM.
├── integrations        Any piece of code that hooks into WordPress.
│    ├── admin          Integrations that load only on the admin.
│    ├── blocks         Integrations that register blocks.
│    ├── front-end      Integrations that load only on the frontend.
│    ├── third-party    Integrations with third-party plugins.
│    └── watchers       Integrations that watch data mutations and do something.
├── loggers             PSR-3 Loggers, see https://www.php-fig.org/psr/psr-3/
├── memoizers           Memoizers cache data and context. @todo move to repositories and remove this concept.
├── models              Idiorm ORM models.
├── oauth               Contains an oauth client. @todo move to a separate lib or to /clients concept.
├── orm                 Contains a wrapper of Idiorm. @todo move to a separate lib or to /wrappers concept.
├── presentations       Presentations lazily and polymorphically generate data for presenters to output.
├── presenters          Presenters output Presentations. In MVVM, our presenters resemble views, where presentations resemble view models.
│    ├── admin          Admin Presenters
│    ├── debug          Debug marker Presenters
│    ├── open-graph     Open Graph Presenters.
│    ├── twitter        Twitter Presenters.
│    └── webmaster      Webmaster tag presenters.
├── routes              Routes register a REST route and connect it to an action.
├── repositories        Repositories are injectable services from which I can request ORM Model instances
├── services            Services offer business rules within a specific functional domain.
├── surfaces            Surfaces are facades through which integrators can interface with Yoast SEO.
├── values              Values are meant to encapsulate data in a reliable structure that is easy to interface with.
├── wordpress           Contains a WordPress wrapper. @todo move to /wrappers concept.
└── wrappers            Wrappers wrap external dependencies for use within our objects.