In a post to the bitExpert.de site Stephan Hochdörfer explains why he thinks that using code over configuration in a DI container is a better approach than static configuration definitions.

In my recent talk on introducing Disco - the DI container with the damn coolest name(tm) - I talk about why I believe that using XML or any other non-code configuration (YAML, JSON, ...) is not a good idea. This stirred some twitter discussion recently which led to this blog post.

Just for the record, for a very long time I was part of the XML camp - just browse my collection of old talks to see for yourself. I praised XML a lot as being the only true DI configuration format.

He then goes through some of the main issues he sees with using something like XML for the dependency container's configuration:

• An XML editor won't give you code-completion for PHP classes or methods.
• Refactoring won't work properly in an XML configuration file.
• An XML editor is not capable of doing proper type checks.
• XML is just too verbose.

For each item he provides a brief explanation and an example of XML where it helps to illustrate the point.

On the SitePoint PHP blog there's a tutorial posted giving you a "fresh look at dependency injection" using the Disco library from bitExpert.

Dependency Injection is all about code reusability. It’s a design pattern aiming to make high-level code reusable, by separating the object creation / configuration from usage.

[...] Our very own Alejandro Gervasio has explained the DI concept fantastically, and Fabien Potencier also covered it in a series. There’s one drawback to this pattern, though: when the number of dependencies grows, many objects need to be created/configured before being passed into the dependent objects. [...] In this article, we’ll demonstrate the concept [of a dependency injection container] further with a newcomer in this field: Disco.

He starts with the installation of the library via Composer and starting up the built-in PHP web server for testing. With that up and running he shows you how to create an instance of the container and set up a sample service with the configuration in the docblock comments. The tutorial then talks about the service scopes, container parameters and shows it in action to create a simple controller handling frontend. There's a bit more about configuration, the container builder functionality and the creation of a response listener when routes are requested.