The Routing Component

Before we start diving into the Routing component, let's refactor our current framework just a little to make templates even more readable:

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// example.com/web/front.php
require_once __DIR__.'/../vendor/autoload.php';

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

$request = Request::createFromGlobals();

$map = [
    '/hello' => 'hello',
    '/bye'   => 'bye',
];

$path = $request->getPathInfo();
if (isset($map[$path])) {
    ob_start();
    extract($request->query->all(), EXTR_SKIP);
    include sprintf(__DIR__.'/../src/pages/%s.php', $map[$path]);
    $response = new Response(ob_get_clean());
} else {
    $response = new Response('Not Found', 404);
}

$response->send();

As we now extract the request query parameters, simplify the hello.php template as follows:

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<!-- example.com/src/pages/hello.php -->
Hello <?= htmlspecialchars($name ?? 'World', ENT_QUOTES, 'UTF-8') ?>

Now, we are in good shape to add new features.

One very important aspect of any website is the form of its URLs. Thanks to the URL map, we have decoupled the URL from the code that generates the associated response, but it is not yet flexible enough. For instance, we might want to support dynamic paths to allow embedding data directly into the URL (e.g. /hello/Fabien) instead of relying on a query string (e.g. /hello?name=Fabien).

To support this feature, add the Symfony Routing component as a dependency:

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$ composer require symfony/routing

Instead of an array for the URL map, the Routing component relies on a RouteCollection instance:

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use Symfony\Component\Routing\RouteCollection;

$routes = new RouteCollection();

Let's add a route that describes the /hello/SOMETHING URL and add another one for the simple /bye one:

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use Symfony\Component\Routing\Route;

$routes->add('hello', new Route('/hello/{name}', ['name' => 'World']));
$routes->add('bye', new Route('/bye'));

Each entry in the collection is defined by a name (hello) and a Route instance, which is defined by a route pattern (/hello/{name}) and an array of default values for route attributes (['name' => 'World']).

Based on the information stored in the RouteCollection instance, a UrlMatcher instance can match URL paths:

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use Symfony\Component\Routing\Matcher\UrlMatcher;
use Symfony\Component\Routing\RequestContext;

$context = new RequestContext();
$context->fromRequest($request);
$matcher = new UrlMatcher($routes, $context);

$attributes = $matcher->match($request->getPathInfo());

The match() method takes a request path and returns an array of attributes (notice that the matched route is automatically stored under the special _route attribute):

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$matcher->match('/bye');
/* Result:
[
    '_route' => 'bye',
];
*/

$matcher->match('/hello/Fabien');
/* Result:
[
    'name' => 'Fabien',
    '_route' => 'hello',
];
*/

$matcher->match('/hello');
/* Result:
[
    'name' => 'World',
    '_route' => 'hello',
];
*/

The URL matcher throws an exception when none of the routes match:

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$matcher->match('/not-found');

// throws a Symfony\Component\Routing\Exception\ResourceNotFoundException

With this knowledge in mind, let's write the new version of our framework:

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// example.com/web/front.php
require_once __DIR__.'/../vendor/autoload.php';

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing;

$request = Request::createFromGlobals();
$routes = include __DIR__.'/../src/app.php';

$context = new Routing\RequestContext();
$context->fromRequest($request);
$matcher = new Routing\Matcher\UrlMatcher($routes, $context);

try {
    extract($matcher->match($request->getPathInfo()), EXTR_SKIP);
    ob_start();
    include sprintf(__DIR__.'/../src/pages/%s.php', $_route);

    $response = new Response(ob_get_clean());
} catch (Routing\Exception\ResourceNotFoundException $exception) {
    $response = new Response('Not Found', 404);
} catch (Exception $exception) {
    $response = new Response('An error occurred', 500);
}

$response->send();

There are a few new things in the code:

• Route names are used for template names;
• 500 errors are now managed correctly;
• Request attributes are extracted to keep our templates simple:

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// example.com/src/pages/hello.php
Hello <?= htmlspecialchars($name, ENT_QUOTES, 'UTF-8') ?>

• Route configuration has been moved to its own file:

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  // example.com/src/app.php
  use Symfony\Component\Routing;
  
  $routes = new Routing\RouteCollection();
  $routes->add('hello', new Routing\Route('/hello/{name}', ['name' => 'World']));
  $routes->add('bye', new Routing\Route('/bye'));
  
  return $routes;

We now have a clear separation between the configuration (everything specific to our application in app.php) and the framework (the generic code that powers our application in front.php).

With less than 30 lines of code, we have a new framework, more powerful and more flexible than the previous one. Enjoy!

Using the Routing component has one big additional benefit: the ability to generate URLs based on Route definitions. When using both URL matching and URL generation in your code, changing the URL patterns should have no other impact. You can use the generator this way:

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use Symfony\Component\Routing;

$generator = new Routing\Generator\UrlGenerator($routes, $context);

echo $generator->generate('hello', ['name' => 'Fabien']);
// outputs /hello/Fabien

The code should be self-explanatory; and thanks to the context, you can even generate absolute URLs:

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use Symfony\Component\Routing\Generator\UrlGeneratorInterface;

echo $generator->generate(
    'hello',
    ['name' => 'Fabien'],
    UrlGeneratorInterface::ABSOLUTE_URL
);
// outputs something like http://example.com/somewhere/hello/Fabien

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use Symfony\Component\Routing\Matcher\CompiledUrlMatcher;
use Symfony\Component\Routing\Matcher\Dumper\CompiledUrlMatcherDumper;

// $compiledRoutes is a plain PHP array that describes all routes in a performant data format
// you can (and should) cache it, typically by exporting it to a PHP file
$compiledRoutes = (new CompiledUrlMatcherDumper($routes))->getCompiledRoutes();

$matcher = new CompiledUrlMatcher($compiledRoutes, $context);