In this new post to his blog today Sam Hennessy continues his "dependency injection manifesto" series and shares why he wants it. The previous parts talked about what DI is and what he wanted from it. This time he talks about why he wants it included.

A DI framework is predominantly interested in the creating and plumbing together of objects. The work of creating and plumbing together objects is mostly very simple, as such do don’t need a framework to do any of it. [...] In the end, the reasoning for using a DI framework should be the same reasoning for use of any library or framework.

He breaks it down into a series of reasons why it would be beneficial to the general PHP development community:

• Increased usability
• Easier to maintain
• Makes for simpler unit testing
• Less invasive code
• Removing the need for boilerplate code

There's lots more good stuff in there than this, so be sure to check out the rest of the post for more of his thoughts.