Adding a Service to Elgg

The services guide has general information about using Elgg services.

To add a new service object to Elgg:

  1. Annotate your class as @internal if it is an internal service.

  2. Open the class Elgg\Di\InternalContainer and/or Elgg\Di\PublicContainer.

  3. Add a @property-read annotation for your service at the top. This allows IDEs and static code analyzers to understand the type of the property when using _elgg_services() or elgg().

  4. Register your service in engine\internal_services.php or engine\public_services.php using autowiring or with a factory.

Inject your dependencies

Elgg uses PHP-DI for registering and resolving services. Dependencies can be autowired (based on the typehinted constructor argument services can be injected) or a service can be constructed in a factory.


For more information about PHP-DI visit their website.

Making a service part of the public API

If your service is meant for use by plugin developers:

  1. Make an interface Elgg\Services\<Name> that contains only those methods needed in the public API.

  2. Have your service class implement that interface.

  3. For methods that are in the interface, move the documentation to the interface. You can simply use {@inheritdoc} in the PHPDocs of the concrete class methods.

  4. Document your service in docs/guides/services.rst (this file).

  5. Open the PHPUnit test Elgg\ApplicationTest and add your service key to the $names array in testServices().

  6. Open the class Elgg\Application.

  7. Add @property-read declaration to document your service, but use your interface as the type, not your service class name.

Now your service will be available via property access on the Elgg\Application instance:

// using the public foo service
$three = elgg()->foo->add(1, 2);


For examples, see the config service, including the interface Elgg\Services\Config and the concrete implementation Elgg\Config.

Service Life Cycle and Factories

By default, services registered on the service provider are „shared“, meaning the service provider will store the created instance for the rest of the request, and serve that same instance to all who request the property.

If you need developers to be able to construct objects that are pre-wired to Elgg services, you may need to add a public factory method to Elgg\Application. Here’s an example that returns a new instance using internal Elgg services:

public function createFoo($bar) {
    $logger = $this->services->logger;
    $db = $this->services->db;
    return new Elgg\Foo($bar, $logger, $db);