docs

docs/components/http-handler/index.md

@@ -23,8 +23,34 @@ use SonsOfPHP\Component\HttpHandler\MiddlewareStack;
 $stack = new MiddlewareStack();
 $stack->add(new RouterMiddleware());
 $stack->add(new CookieMiddleware());
+$stack->add(function ($request, $handler) {
+    // ...
+});
 // ...
 
 $app = new HttpHandler($stack);
 $response = $app->handle($request);
 ```
+
+The `MiddlewareStack` accepts objects that implement `Psr\Http\Server\MiddlewareInterface`
+and anonymous functions.
+
+### Middleware Priorities
+
+An optional second argument may be passed to the `MiddlewareStack` which is for
+the priority of the middleware. Priorities are ordered in ascending order.
+
+```php
+<?php
+
+use SonsOfPHP\Component\HttpHandler\MiddlewareStack;
+
+$stack = new MiddlewareStack();
+$stack->add(new NotFoundMiddleware(), 1025);
+$stack->add(new RouterMiddleware(), 255);
+$stack->add(new CookieMiddleware(), -255);
+$stack->add(new DefaultMiddleware());
+```
+
+In the above example, the `CookieMiddleware` will be processed first and
+`NotFoundMiddleware` will be processed last.