Building a PHP Framework: Part 8 - Routing

Originally posted on DevelopmentMatt.com

Part 7 got us up to speed on the container that will be used in the Analyze PHP Framework. In this post we'll cover how routing works in general and specifically within PHP.

How Routing Works

Routing is the process of parsing a URI and determining the appropriate action to take.

For example, consider the following URI:

https://example.com/login

How does a request like the one above result in a response to the user? Let's break it down:

1. The request is received by the application.

2. The application breaks down the request into its components. Things like: the method (ex: GET), host, path, etc.

3. The application looks for a defined route that matches this request.

4. Once found, it takes the defined action and returns a response.

A Laravel Example

For a real-world example, here's one way the above example could be implemented in Laravel.

Route::get('/login', function() {
    return view('login');
});

We define a GET route for the /login URI. When that route is requested we return a response – in this case, HTML for the login page.

How Routers Work

There are a number of routers in the PHP ecosystem. They range from the more simplistic to feature-packed behemoths. Although they differ in size and complexity, they generally employ the same fundamental steps: parse the request, match the pattern, run some code, return a response.

The Symfony router (probably the most widely used PHP router) does this.

As does this one.

And this one.

A Very Simple PHP Router

To demonstrate these concepts let's create a stupid simple, not at all useful, PHP router.

<?php
/**
 * First, let's define our Router object.
 */
class Router
{
    /**
     * The request we're working with.
     *
     * @var string
     */
    public $request;

    /**
     * The $routes array will contain our URI's and callbacks.
     * @var array
     */
    public $routes = [];

    /**
     * For this example, the constructor will be responsible
     * for parsing the request.
     *
     * @param array $request
     */
    public function __construct(array $request)
    {
        /**
         * This is a very (VERY) simple example of parsing
         * the request. We use the $_SERVER superglobal to
         * grab the URI.
         */
        $this->request = basename($request['REQUEST_URI']);
    }

    /**
     * Add a route and callback to our $routes array.
     *
     * @param string   $uri
     * @param Callable $fn
     */
    public function addRoute(string $uri, \Closure $fn) : void
    {
        $this->routes[$uri] = $fn;
    }

    /**
     * Determine is the requested route exists in our
     * routes array.
     *
     * @param  string  $uri
     * @return boolean
     */
    public function hasRoute(string $uri) : bool
    {
        return array_key_exists($uri, $this->routes);
    }

    /**
     * Run the router.
     *
     * @return mixed
     */
    public function run()
    {
        if($this->hasRoute($this->request)) {
            $this->routes[$this->request]->call($this);
        }
    }
}

/**
 * Create a new router instance.
 */
$router = new Router($_SERVER);

/**
 * Add a "hello" route that prints to the screen.
 */
$router->addRoute('hello', function() {
    echo 'Well, hello there!!';
});

/**
 * Run it!
 */
$router->run();

Run The Code

1. Save this code locally as index.php.
2. In your terminal navigate to the directory where you saved the script.
3. Start the built-in PHP web server: php -S localhost:1234
4. In your browser go to: http://localhost:1234/hello

Conclusion

I've touched on the very basics of routing, shared some routing examples from the PHP world, and built a extremely simple router. On a related note, I've started work on the router that will be used in the Analyze PHP framework. To keep up to speed on it, be sure to follow @AnalyzePHP on Twitter.

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