Request Lifecycle for a Mezzio-Based Application

The request lifecycle is the sequence of steps that happen from the moment a user makes an HTTP request until the server sends back a response.

The application bootstraps and loads configuration to create the Mezzio application instance, registers factories, aliases and delegators in the service container, reads all available routes with their allowed request methods and registers them (managed by FastRoute), and loads the predefined order of middleware in the pipeline.

FastRoute matches the incoming URL and method against the registered routes, for example matching a GET request to /page/about against the GetPageViewHandler handler under the route name page::about.

The matched route name is extracted from the request attribute and passed to the renderer, using code similar to $template = $request->getAttribute(RouteResult::class)->getMatchedRouteName();, after which the handler executes the custom business logic.

Twig loads the matched template file, applies the layout it extends, renders its blocks, and includes any partials, producing the final HTML output.

An HtmlResponse is created with a status code, headers, and the rendered HTML body. It then flows back through the middleware stack in reverse (the response pipeline), where middleware can modify headers, cookies, or compress content, before the response emitter sends the final response back to the browser as HTTP 20x/30x, 40x, or 50x.