For the Invoice Management System application, we need to have routing of requests. Routing will help us to implement pages independently from each other and be rendered via a handler such as a PHP custom function or even better – An Action Controller PHP class. In this post, we are going to implement a simple router functionality so we can handle HTTP GET requests and render different information based on the page we are currently in.

The Request Class

The Request class provides a set of methods that are used in the Router class for identifying a callback function. With the help of the parse_url() function we can get an associated array of elements from a current URL. The URL is located in the $_SERVER[‘REQUEST_URI’] global array.

<?php declare(strict_types=1);

namespace Invoice;

class Request
{
    private array $server;

    public function __construct()
    {
        $this->server = $_SERVER;
    }

    public function getServer(string $name): mixed
    {
        return $this->server[$name] ?? null;
    }

    public function getUri(): array
    {
        return parse_url($this->getServer('REQUEST_URI'));
    }

    public function getPath(): string
    {
        $uri = $this->getUri();
        return $uri['path'];
    }
}

The Router Class

The Router class is responsible for finding or dispatching an incoming HTTP request and returning a callback function that is triggered in the App::run() method. For simplicity, we are going to hard-code the list of routes inside the dispatch() method. Later, we are going to move the list of routes to a separate config file.

<?php declare(strict_types=1);

namespace Invoice;

class Router
{
    public function dispatch(Request $request): mixed
    {
        $path = $request->getPath();

        $routes = [
            '/' => function () {
                echo 'Home Page';
            },
            '/invoices' => function () {
                echo 'Invoices';
            },
            '/settings' => function () {
                echo 'Settings';
            }
        ];

        return $routes[$path] ?? null;
    }
}

Putting Everything Together

The App::run() method is responsible for instantiating the Request and Router classes. The Request object is passed as an argument of the Router::dispatch() method.

<?php declare(strict_types=1);

namespace Invoice;

class App
{
    public function run(): void
    {
        $router = new Router();

        $request = new Request();
        $handler = $router->dispatch($request);

        if ($handler) {
            $handler();
        }
    }
}

The dispatch() method returns a handler function that is later executed inside the run() method. As a result, we render different content based on the request path information provided by the Request::getPath() method.

Service Container

Both Request and Router classes may also be instantiated via the Service Container class that is responsible for managing dependencies. As for a simple PHP routing implementation, we aren’t going to add a service container. A separate post, however, will cover the service container topic.

And Finally…

You may watch a video tutorial with an additional explanation of the simple PHP router implementation. This video is a part of videos dedicated to the creation of the Invoice Management System.

All source code from this post can be found on GitHub.