dependency-injection-container | A small Dependency Injection Container pattern in PHP | Dependency Injection library

I've spent a lot of time reading these articles (along with many others):

• Mark Seemann - Pure DI

• Mark Seemann - When to use a DI Container

• Mark Seemann - Compose object graphs with confidence

• Mark Seemann - Don't call the container; it'll call you

• Mark Seemann - Understanding the Composition Root

and I'm still trying to wrap my head around DI and the concept of "wiring up the dependencies" and the "auto wiring" functionality of an IoC container.

I think I understand the theory of Dependency Injection and Inversion of Control and I've implemented the example shown here from 2016 (I updated the code to use PSR-11 and eliminate the need for the container-interop package):

• https://www.sitepoint.com/how-to-build-your-own-dependency-injection-container/

The application of the container example is shown at the GitHub link: https://github.com/sitepoint-editors/Container .

Note that while this example uses PHP, I'm trying to understand the details of DI independently from language, so any language is welcome.

Can someone explain the difference between manually wiring up dependencies, and using a container's auto wiring functionality? The SitePoint article briefly mentions that more advanced containers add the automatic wiring functionality, implying that the example doesn't contain this function already. Can someone explain the application shown on the GitHub page and how that relates to core DI and IoC concepts, like the Composition Root.