New in Symfony 5.3: Runtime Component

Contributed by Nicolas Grekas in #38465 and #40513

Symfony 5.3 was released on May 31, 2021. Although we've published many articles about new Symfony 5.3 features, there are some interesting new features that we haven't discussed yet. The first one is the new Runtime Component.

The purpose of the Runtime component is to abstract most of the application bootstrapping logic into so-called runtimes, allowing you to write generic front-controllers. This will make Symfony applications easier to maintain, because the front-controller code can be moved to a Symfony Flex recipe managed automatically by Symfony.

In addition, this component decouples the bootstrapping from any global state to make sure the application can run with runtimes like PHP-FPM, ReactPHP, Swoole, etc. without any changes.

If you open your public/index.php file, you'll see some code like this:

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// public/index.php
<?php

use App\Kernel;
use Symfony\Component\Dotenv\Dotenv;
use Symfony\Component\ErrorHandler\Debug;
use Symfony\Component\HttpFoundation\Request;

require dirname(__DIR__).'/vendor/autoload.php';

(new Dotenv())->bootEnv(dirname(__DIR__).'/.env');

if ($_SERVER['APP_DEBUG']) {
    umask(0000);
    Debug::enable();
}

$kernel = new Kernel($_SERVER['APP_ENV'], (bool) $_SERVER['APP_DEBUG']);
$request = Request::createFromGlobals();
$response = $kernel->handle($request);
$response->send();
$kernel->terminate($request, $response);

In addition to some autoloading and configuration, this file contains the code needed to process the well-known Symfony Request-Response flow. In a new Symfony 5.3 application, the same front-controller uses Symfony Runtime and its code looks as follows:

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// public/index.php
<?php

use App\Kernel;

require_once dirname(__DIR__).'/vendor/autoload_runtime.php';

return function (array $context) {
    return new Kernel($context['APP_ENV'], (bool) $context['APP_DEBUG']);
};

Why is the new front-controller code so concise? Where is the request turned into a response? What's this autoload_runtime.php file? Read the new Runtime component docs to learn about all this and more. You will also learn how to tweak this runtime and how to create your own runtimes.

If you are upgrading an existing application to Symfony 5.3, you can start using this new component as follows:

• Install the component by running composer require symfony/runtime
• Update your front controller using the public/index.php code found in Symfony's FrameworkBundle recipe
• Update your console script using the bin/console code found in Symfony's Console recipe

If you want to learn more about this component, join the SymfonyWorld Online 2021 Summer Edition conference (June 17-18, 2021), where Tobias Nyholm will deliver a talk titled "Runtime component: The game changer".