Middleware and Events

Middleware implements Fetch\Interfaces\Middleware:

handle(
    RequestInterface $request,
    callable $next,
): ResponseInterface|PromiseInterface

Callables with that shape are accepted too. Add with addMiddleware() and remove/replace through the handler's middleware methods. Middleware participates in the buffered request pipeline and may receive a promise when async mode is active.

Event-aware clients and handlers provide on() and convenience registrations for request, response, error, retry, timeout, and redirect events. Event classes live in Fetch\Events. Middleware can change execution; events are lifecycle notifications. Exact signatures are declared in Fetch\Interfaces\MiddlewareAware and EventAware.