add perfomance chapters

implementation/18-caching/data/pages/06-router.md

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+[<< previous](05-http.md) | [next >>](07-dispatching-to-a-class.md)
+
+### Router
+
+A router dispatches to different handlers depending on rules that you have set up.
+
+With your current setup it does not matter what URL is used to access the application, it will always result in the same
+response. So let's fix that now.
+
+I will use [nikic/fast-route](https://github.com/nikic/FastRoute) in this tutorial. But as always, you can pick your own
+favorite package.
+
+Alternative packages: [symfony/Routing](https://github.com/symfony/Routing), [Aura.Router](https://github.com/auraphp/Aura.Router), [fuelphp/routing](https://github.com/fuelphp/routing), [Klein](https://github.com/chriso/klein.php)
+
+By now you know how to install Composer packages, so I will leave that to you.
+
+Now add this code block to your `Bootstrap.php` file where you added the 'hello world' message in the last chapter.
+
+```php
+$dispatcher = \FastRoute\simpleDispatcher(function (\FastRoute\RouteCollector $r) {
+    $r->addRoute('GET', '/hello[/{name}]', function (\Psr\Http\Message\ServerRequestInterface $request) {
+        $name = $request->getAttribute('name', 'Stranger');
+        $response = (new \Laminas\Diactoros\Response)->withStatus(200);
+        $response->getBody()->write('Hello ' . $name . '!');
+        return $response;
+    });
+    $r->addRoute('GET', '/another-route', function (\Psr\Http\Message\ServerRequestInterface $request) {
+        $response = (new \Laminas\Diactoros\Response)->withStatus(200);
+        $response->getBody()->write('This works too!');
+        return $response;
+    });
+});
+
+$routeInfo = $dispatcher->dispatch(
+    $request->getMethod(),
+    $request->getUri()->getPath(),
+);
+
+switch ($routeInfo[0]) {
+    case \FastRoute\Dispatcher::METHOD_NOT_ALLOWED:
+        $response = (new \Laminas\Diactoros\Response)->withStatus(405);
+        $response->getBody()->write('Method not allowed');
+        $response = $response->withStatus(405);
+        break;
+    case \FastRoute\Dispatcher::FOUND:
+        $handler = $routeInfo[1];
+        foreach ($routeInfo[2] as $attributeName => $attributeValue) {
+            $request = $request->withAttribute($attributeName, $attributeValue);
+        }
+        /** @var \Psr\Http\Message\ResponseInterface $response */
+        $response = call_user_func($handler, $request);
+        break;
+    case \FastRoute\Dispatcher::NOT_FOUND:
+    default:
+        $response = (new \Laminas\Diactoros\Response)->withStatus(404);
+        $response->getBody()->write('Not Found!');
+        break;
+}
+```
+
+In the first part of the code, you are registering the available routes for your application. In the second part, the
+dispatcher gets called and the appropriate part of the switch statement will be executed. If a route was found, 
+we collect any variable parameters of the route, store them in the request parameterbag and call the handler callable.
+If the route dispatcher returns a wrong value in the first entry of the routeMatch array we handle it the same as a 404.
+
+This setup might work for really small applications, but once you start adding a few routes your bootstrap file will
+quickly get cluttered. So let's move them out into a separate file.
+
+Create a new directory in you projectroot named 'config' and add a 'routes.php' file with the following content;
+
+```php
+<?php declare(strict_types = 1);
+
+return function(\FastRoute\RouteCollector $r) {
+    $r->addRoute('GET', '/hello[/{name}]', function (\Psr\Http\Message\ServerRequestInterface $request) {
+        $name = $request->getAttribute('name', 'Stranger');
+        $response = (new \Laminas\Diactoros\Response)->withStatus(200);
+        $response->getBody()->write('Hello ' . $name . '!');
+        return $response;
+    });
+    $r->addRoute('GET', '/another-route', function (\Psr\Http\Message\ServerRequestInterface $request) {
+        $response = (new Laminas\Diactoros\Response)->withStatus(200);
+        $response->getBody()->write('This works too!');
+        return $response;
+    });
+};
+```
+
+Now let's rewrite the route dispatcher part to use the `Routes.php` file.
+
+```php
+$routeDefinitionCallback = require __DIR__ . '/../config/routes.php';
+$dispatcher = \FastRoute\simpleDispatcher($routeDefinitionCallback);
+```
+
+This is already an improvement, but now all the handler code is in the `routes.php` file. This is not optimal, so let's fix that in the next part.
+
+Of course we now need to add the 'config' folder to the configuration files of our
+devhelpers so that they can scan that directory as well.
+
+[<< previous](05-http.md) | [next >>](07-dispatching-to-a-class.md)