Sergey Zhuk has a new post to his site showing how to define and use middleware in your ReactPHP application.

What exactly is middleware? In real application when the request comes to the server it has to go through the different request handlers. For example, it could be authentication, validation, ACL, logger, caching and so on. Consider the request-response circle as an onion and when a request comes in, it has to go through the different layers of this onion, to get to the core. And every middleware is a layer of the onion.

He starts off with a simple example of a ReactPHP-based server that just responds to all requests with a "Hello world" message. I includes some logging functionality that he then refactors out into middleware. This logging records the HTTP method used, time of the request and the URL requested - all things the code can get from the request object. Code is included showing the refactoring out to the middleware and injecting it into the ReactPHP application. He then updates it to check for the existence of a file and, if so, returns the results as a stream. Finally he covers updates to the response inside the middleware, changing the HTTP status code and content returned based on the results of various checks.