Introduction to Silex – A Symfony Micro-framework

Silex is a PHP micro-framework based on Symfony components and inspired by the Sinatra Ruby framework. In this article, we are going to get started with the framework and see the how it fits our needs.

Logo

Installation

The best and recommended way to install Silex is through composer:

// composer.json
{
    "require": {
        "silex/silex": "1.3.*@dev",
        "twig/twig": "1.17.*@dev"
    },
    "require-dev": {
        "symfony/var-dumper": "dev-master"
    }
}

Run composer update --dev to load the dependencies and generate the autoloader. We also required twig because we want to use it as our template engine, and the new var-dumper from Symfony as a development dependency – read more about it here.

Creating a Folder Structure

One of the things I like about Silex is that it gives you a bare bones framework that you can organize in any way you want.

|-app/
|----config/
|-resources/
|----views/
|----logs/
|-src/
|----MyApp/
|-public/
|----index.php
|----.htaccess
|-vendor/
|-composer.json

For instance, I don’t like my root application folder to be called web, I prefer the normal public folder. The src directory is where we put our application specific code while the other folders are rather self explanatory.

Our public/index.php file will create a new Silex\Application which is our app container instance, and this is where we are going to wire the components.

// public/index.php
<?php

require_once __DIR__ . '/../vendor/autoload.php';

$app = new Silex\Application();

$app->run();

Now if you hit your root application URL, you should see a page not found error. You can turn on debugging by setting the debug mode in the container to true.

If you are having problems accessing your routes, make sure that your server document root is pointing to the public folder. You can check the doc for more info about configuring your webserver.

// public/index.php

//...

$app['debug'] = true;

$app->run();

Now if we try again we get a descriptive NotFoundHttpException, because we didn’t register any routes.

Routing

Registering a route is straightforward, you simply map a URL pattern to a controller function.

// public/index.php
$app->get('/', function(){
	return "Hello world";
});

We can handle get, post, put and delete, or we can use the match method to handle any request method. The handle function must return either a string or a Symfony\Component\HttpFoundation\Response instance.

// public/index.php
$app->get('/', function(){
	return new Symfony\Component\HttpFoundation\Response("Hello world");
});

Routing Parameters

$app->get("/users/{id}", function($id){
   return "User - {$id}";
});

We can add multiple parameters to the URL pattern, the only convention is that the name of the URL pattern parameter must match the name used in the function, or you’ll get a RuntimeException. You can also specify a URL pattern using the assert method, and a default value using the value method.

$app->get("/users/{id}", function($id){
   return "User - {$id}";
})
    ->value("id", 0) //set a default value
    ->assert("id", "\d+"); // make sure the id is numeric

One of my favorite route methods is convert: it allows us to intercept the request and change the parameter value before passing it to the callback function.

$app->get("/users/{user}", function($user){
    // return the user profile
    
    return "User {$user}";
})->convert("user", function($id){
        $userRepo = new User();
        $user = $userRepo->find($id);

        if(!$user){
            return new Response("User #{$id} not found.", 404);
        }

        return $user;
    });

In this example, the convert method takes a user id, looks up the database and returns the user. A 404 response is returned if the user is not found.

If you are a Laravel fan, you are used to filters like auth, csrf and guest. In Silex, however, you can provide a callback function to behave like a filter.

$app->get("/users/{user}", function($user){
    // return the user profile

    return "User {$user}";
})->before(function($request, $app){
    // redirect if the user is not logged in
})
->after(function($request, $response){
    // log request events
})
->finish(function(){
    // log request event
});

Similarly, you can use the after and finish methods. But keep in mind that the finish method doesn’t have access to the request and response because the response is already sent to the user.

Named Routes

When dealing with multiple routes it makes sense to name them descriptively. This can be helpful when updating the URL format or generating template links.

$app->get("/users/list", function(Silex\Application $app){
    return "List of users";
})->bind('users');

If you are using the URL Generator Service Provider, you can generate a link directly to the route.

<a href="{{ app.url_generator.generate('users') }}">Users</a>

Controllers

In real world applications, we don’t use closures for routing, but rather create separate controller classes to handle the requests.

$app->get("/", "MyApp\Controller\HomeController::index");

Grouping Controllers

One of the main benefits of using class controllers is the ability to group them. When creating a RESTful API, the URL’s will be something like this:

  • /users
  • /users/id [PUT, DELETE]
  • /users/id/edit

A really clean way to deal with this is to group the controllers into something called controller providers. Our User controller provider must implement the ControllerProviderInterface and define the connect method.

// src/MyApp/Controller/Provider/User.php

class User implements ControllerProviderInterface{

    public function connect(Application $app)
    {
        $users = $app["controllers_factory"];

        $users->get("/", "MyApp\\Controller\\UserController::index");

        $users->post("/", "MyApp\\Controller\\UserController::store");

        $users->get("/{id}", "MyApp\\Controller\\UserController::show");

        $users->get("/edit/{id}", "MyApp\\Controller\\UserController::edit");

        $users->put("/{id}", "MyApp\\Controller\\UserController::update");

        $users->delete("/{id}", "MyApp\\Controller\\UserController::destroy");

        return $users;
    }

}

The $app['controllers_factory'] returns a new Silex\ControllerCollection which holds our routing collection. The UserController will handle the registered requests.

// src/MyApp/Controller/UserController.php

class UserController{

    public function index(){
        // show the list of users
    }

    public function edit($id){
        // show edit form
    }

    public function show($id){
        // show the user #id
    }

    public function store(){
        // create a new user, using POST method
    }
    
    public function update($id){
        // update the user #id, using PUT method
    }

    public function destroy($id){
        // delete the user #id, using DELETE method
    }
}

The only remaining part is to attach our controller collection to our application. When working with routes, I prefer the Laravel approach of registering them inside a separate file and including them.

// app/routes.php

$app->mount("/users", new \MyApp\Controller\Provider\User());

The mount method takes the prefix and our User provider class as parameters.

Additionally, one of the benefits of using controller collections is the ability to use the before, after and finish filters without having to call them on every route.

// src/MyApp/Controller/Provider/User.php

class User implements ControllerProviderInterface{

    public function connect(Application $app)
    {
        //...
        $users->before(function(){
		// check for something here
	});
    }
}

Providers

We mentioned this term before but it simply stands for a small class that ties a component to the Silex application. There is a list of pre-included providers and, to use one, you simply register it to the application instance.

// app/providers.php
$app->register(new Silex\Provider\TwigServiceProvider(), array(
    'twig.path' => __DIR__.'/../views',
));

Of course this should be done after requiring Twig inside your composer and updating dependencies. Now if you visit the TwigServiceProvider::register method you can see that we can access the Twig_Environment from the container.

$app->get(function(){
   return $app['twig']->render('home.twig');
});

To create your own provider for Silex, you need to implement the Silex\ServiceProviderInterface and define the register method. You can read more in the doc.

Conclusion

Silex is a small and fast framework for Symfony fans. This introduction is aimed at getting you on board and trying the framework. We didn’t cover everything but hopefully I can make you exited to give it a go. If you have any questions or opinions let me know in the comments!

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