Flex: Compose your Application

Symfony: Start Micro!

Unless you're building a pure API (more on that soon!), you'll probably want to render HTML. To do that, you'll use Twig. Twig is a flexible, fast, and secure template engine for PHP. It makes your templates more readable and concise; it also makes them more friendly for web designers.

Is Twig already installed in our application? Actually, not yet! And that's great! When you start a new Symfony project, it's small: only the most critical dependencies are included in your composer.json file:

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"require": {
    "...",
    "symfony/console": "^6.1",
    "symfony/flex": "^2.0",
    "symfony/framework-bundle": "^6.1",
    "symfony/yaml": "^6.1"
}

This makes Symfony different from any other PHP framework! Instead of starting with a bulky app with every possible feature you might ever need, a Symfony app is small, simple and fast. And you're in total control of what you add.

Flex Recipes and Aliases

So how can we install and configure Twig? By running one single command:

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$ composer require twig

Two very interesting things happen behind the scenes thanks to Symfony Flex: a Composer plugin that is already installed in our project.

First, twig is not the name of a Composer package: it's a Flex alias that points to symfony/twig-bundle. Flex resolves that alias for Composer.

And second, Flex installs a recipe for symfony/twig-bundle. What's a recipe? It's a way for a library to automatically configure itself by adding and modifying files. Thanks to recipes, adding features is seamless and automated: install a package and you're done!

You can find a full list of recipes and aliases inside RECIPES.md on the recipes repository.

What did this recipe do? In addition to automatically enabling the feature in config/bundles.php, it added 3 things:

config/packages/twig.yaml

A configuration file that sets up Twig with sensible defaults.

config/packages/test/twig.yaml

A configuration file that changes some Twig options when running tests.

templates/

This is the directory where template files will live. The recipe also added a base.html.twig layout file.

Twig: Rendering a Template

Thanks to Flex, after one command, you can start using Twig immediately:

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<?php
  // src/Controller/DefaultController.php
  namespace App\Controller;

  use Symfony\Component\Routing\Attribute\Route;
  use Symfony\Component\HttpFoundation\Response;
+ use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;

- class DefaultController
+ class DefaultController extends AbstractController
  {
       #[Route('/hello/{name}', methods: ['GET'])]
       public function index(string $name): Response
       {
-        return new Response("Hello $name!");
+        return $this->render('default/index.html.twig', [
+            'name' => $name,
+        ]);
       }
  }

By extending AbstractController, you now have access to a number of shortcut methods and tools, like render(). Create the new template:

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{# templates/default/index.html.twig #}
<h1>Hello {{ name }}</h1>

That's it! The {{ name }} syntax will print the name variable that's passed in from the controller. If you're new to Twig, welcome! You'll learn more about its syntax and power later.

But, right now, the page only contains the h1 tag. To give it an HTML layout, extend base.html.twig:

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{# templates/default/index.html.twig #}
{% extends 'base.html.twig' %}

{% block body %}
    <h1>Hello {{ name }}</h1>
{% endblock %}

This is called template inheritance: our page now inherits the HTML structure from base.html.twig.

Profiler: Debugging Paradise

One of the coolest features of Symfony isn't even installed yet! Let's fix that:

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$ composer require profiler

Yes! This is another alias! And Flex also installs another recipe, which automates the configuration of Symfony's Profiler. What's the result? Refresh!

See that black bar on the bottom? That's the web debug toolbar, and it's your new best friend. By hovering over each icon, you can get information about what controller was executed, performance information, cache hits & misses and a lot more. Click any icon to go into the profiler where you have even more detailed debugging and performance data!

Oh, and as you install more libraries, you'll get more tools (like a web debug toolbar icon that shows database queries).

You can now directly use the profiler because it configured itself thanks to the recipe. What else can we install?

Rich API Support

Are you building an API? You can already return JSON from any controller:

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// src/Controller/DefaultController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\JsonResponse;
use Symfony\Component\Routing\Attribute\Route;

class DefaultController extends AbstractController
{
    // ...

    #[Route('/api/hello/{name}', methods: ['GET'])]
    public function apiHello(string $name): JsonResponse
    {
        return $this->json([
            'name' => $name,
            'symfony' => 'rocks',
        ]);
    }
}

But for a truly rich API, try installing API Platform:

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$ composer require api

This is an alias to api-platform/api-pack Symfony pack, which has dependencies on several other packages, like Symfony's Validator and Security components, as well as the Doctrine ORM. In fact, Flex installed 5 recipes!

But like usual, we can immediately start using the new library. Want to create a rich API for a product table? Create a Product entity and give it the #[ApiResource] attribute:

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// src/Entity/Product.php
namespace App\Entity;

use ApiPlatform\Core\Annotation\ApiResource;
use Doctrine\ORM\Mapping as ORM;

#[ORM\Entity]
#[ApiResource]
class Product
{
    #[ORM\Id]
    #[ORM\GeneratedValue(strategy: 'AUTO')]
    #[ORM\Column(type: 'integer')]
    private int $id;

    #[ORM\Column(type: 'string')]
    private string $name;

    #[ORM\Column(type: 'integer')]
    private int $price;

    // ...
}

Done! You now have endpoints to list, add, update and delete products! Don't believe me? List your routes by running:

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$ php bin/console debug:router

------------------------------ -------- -------------------------------------
 Name                           Method   Path
------------------------------ -------- -------------------------------------
 api_products_get_collection    GET      /api/products.{_format}
 api_products_post_collection   POST     /api/products.{_format}
 api_products_get_item          GET      /api/products/{id}.{_format}
 api_products_put_item          PUT      /api/products/{id}.{_format}
 api_products_delete_item       DELETE   /api/products/{id}.{_format}
 ...
------------------------------ -------- -------------------------------------

Removing Recipes

Not convinced yet? No problem: remove the library:

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$ composer remove api

Flex will uninstall the recipes: removing files and undoing changes to put your app back in its original state. Experiment without worry.

More Features, Architecture and Speed

I hope you're as excited about Flex as I am! But we still have one more chapter, and it's the most important yet. I want to show you how Symfony empowers you to quickly build features without sacrificing code quality or performance. It's all about the service container, and it's Symfony's super power. Read on: about The Architecture.