Middleware - airtype/craft-httpmessages GitHub Wiki

What is middleware?

A middleware a class is primarily responsible for receiving a Request and Response object and returning a Response object. Upon receiving a Request and Response object, a middleware can decorate the objects according to the needs of the middleware.

A middleware is also aware of the next middleware in the middleware stack, and is responsible for calling that middleware, passing the decorated Request and Response objects.

For each route defined in the httpmessages.php config, a stack of middleware should be defined as well.

Above is an example of Request and Response objects being passed through a stack of middleware. The ? in the middleware represents an opportunity for the middleware to decorate the Request and Response object, before passing the objects to the next middleware. Likewise, each middleware has the opportunity to decorate the Response object that is returned by the previous middleware.

[Relay] (http://relayphp.com) is utilized for processing the middleware collection. For a more detailed explanation of how it implements middleware, please refer to its documentation.