Create your own framework... on top of the Symfony2 Components (part 4)

Fabien Potencier

January 09, 2012

This article is part of a series of articles that explains how to create a framework with the Symfony Components. It is OBSOLETE but an up-to-date version can be found in the Symfony documentation.

Before we start with today's topic, let's refactor our current framework just a little to make templates even more readable:

 '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:



Hello

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 instead of relying on a query string:

# Before
/hello?name=Fabien

# After
/hello/Fabien

To support this feature, we are going to use the Symfony2 Routing component. As always, add it to composer.json and run the php composer.phar update command to install it:

{
    "require": {
        "symfony/class-loader": "2.1.*",
        "symfony/http-foundation": "2.1.*",
        "symfony/routing": "2.1.*"
    }
}

From now on, we are going to use the generated Composer autoloader instead of our own autoload.php. Remove the autoload.php file and replace its reference in front.php:

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

use Symfony\Component\Routing\RouteCollection;

$routes = new RouteCollection();

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

use Symfony\Component\Routing\Route;

$routes->add('hello', new Route('/hello/{name}', array('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 (array('name' => 'World')).

Read the official documentation -- available soon -- for the Routing component to learn more about its many features like URL generation, attribute requirements, HTTP method enforcements, loaders for YAML or XML files, dumpers to PHP or Apache rewrite rules for enhanced performance, and much more.

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

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

$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):

print_r($matcher->match('/bye'));
array (
  '_route' => 'bye',
);

print_r($matcher->match('/hello/Fabien'));
array (
  'name' => 'Fabien',
  '_route' => 'hello',
);

print_r($matcher->match('/hello'));
array (
  'name' => 'World',
  '_route' => 'hello',
);

Even if we don't strictly need the request context in our examples, it is used in real-world applications to enforce method requirements and more.

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

$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:

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 $e) {
    $response = new Response('Not Found', 404);
} catch (Exception $e) {
    $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:

    

    Hello

  • Routes configuration has been moved to its own file:

    add('hello', new Routing\Route('/hello/{name}', array('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. Want to know how to use the generator? Insanely easy:

use Symfony\Component\Routing;

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

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

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

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

Concerned about performance? Based on your route definitions, create a highly optimized URL matcher class that can replace the default UrlMatcher:

 [php]
 $dumper = new Routing\Matcher\Dumper\PhpMatcherDumper($routes);

 echo $dumper->dump();

Want even more performance? Dump your routes as a set of Apache rewrite rules:

 [php]
 $dumper = new Routing\Matcher\Dumper\ApacheMatcherDumper($routes);

 echo $dumper->dump();