In a new post to his site David Lundgren wonders when dependency injection becomes an anti-pattern when used in PHP applications. The idea of dependency injection is to provide objects with instances of other objects representing things they'll need to get the job done (goes along with separation of concerns). Unfortunately, if used incorrectly, DICs - dependency injection containers - can become less useful and more of a hinderance than a positive part of the application.

During my tenure as a seasoned, and tenderized, PHP developer I have used many design patterns: adapters, factories, data mappers, facades, etc. The most recent one that I have been working with is Dependency Injection. Inversion of Control is not a new idea, at least not in the programming world, but in the PHP world it seems to have taken us by storm in recent years. Every framework will often have a Dependency Injector built in, or offer it as a component for use. It is the hip thing to do in PHP, but I believe we need to take a step back and evaluate it for what we are really trying to achieve. That is reducing the tight coupling that our objects may have. I view it as removing the new-able’s from our objects code, and handing the object creation over to something else to deal with.

He talks about how dependency injection containers and service locators relate to each other. He also suggests that, at the heart of every dependency injection container, there's a service locator. He gives an example of a project where a large number of dependencies are being injected and how, despite the assumption of flexibility, his dependencies don't change that often, making the DIC and its functionality a bit less important.