A few hours ago, we pushed Expressive 1.0.

This is a huge milestone for the ZF3 initiative; I've even called it the cornerstone. It signals a huge shift in direction for the project, returning to its roots as a component library. Expressive itself, however, also signals the future of PHP applications we envision: composed of layered, single-purpose PSR-7 middleware.

As I've surveyed the successes and failures of ZF1 and ZF2, I've started considering how we can address usability: how do we make the framework more approachable?

One concept I've been researching a ton lately is middleware. Middleware exists in a mature form in Ruby (via Rack), Python (via WSGI), and Node (via Connect / ExpressJS); just about every language has some exemplar. Even PHP has some examples already, in StackPHP and Slim Framework.

The basic concept of middleware can be summed up in a single method signature:

function (request, response) { }

The idea is that objects, hashes, or structs representing the HTTP request and HTTP response are passed to a callable, which does something with them. You compose these in a number of ways to build an application.