Installation & Setup
Symfony gives you two common ways to start a new project: the dedicated Symfony CLI installer, or a plain Composer command. Either one downloads a working skeleton application that you then build on top of. This page walks through both, shows how to run the local development server, and introduces Symfony Flex — the Composer plugin that makes installing Symfony packages feel almost automatic.
Installing via the Symfony CLI
The Symfony CLI is a standalone binary (not a Composer package) that manages local development tasks — creating projects, running the dev server, checking requirements, and more. Once it is installed on your machine, creating a full-stack web application is a single command:
symfony new my_project --webapp
The --webapp flag installs the webapp edition: a fuller set of
bundles suited to a traditional web application — Twig for templates, the Doctrine ORM, form
handling, security, and a handful of developer-experience tools already wired in.
Installing via Composer
If you don't want the extra Symfony CLI tool, or you're building something closer to a small API or microservice, Composer alone can create a project from the minimal skeleton edition:
composer create-project symfony/skeleton my_project| Edition | What you get | Best for |
|---|---|---|
--webapp | Twig, Doctrine, forms, security, profiler, and more preinstalled | Full websites and admin-style applications |
symfony/skeleton | Only the bare minimum to boot a Symfony kernel and router | Small APIs and microservices where you add packages as you need them |
Starting the Development Server
Once inside your project folder, the Symfony CLI's built-in web server is the quickest way to preview your application, complete with a locally trusted TLS certificate:
cd my_project
symfony server:start
By default this serves your application at https://127.0.0.1:8000. The first time you
run it, the CLI may offer to install a local certificate authority so the https URL
doesn't show a browser warning.
What Is Symfony Flex?
Symfony Flex is a Composer plugin that ships with every new Symfony project. When
you run composer require for a supported package, Flex looks up a matching
recipe and automatically drops in the configuration files, bundle registration,
and boilerplate that package needs — instead of you wiring it up by hand.
composer require twig
Behind that one command, Flex may register the TwigBundle, create a
config/packages/twig.yaml, and add a templates/ folder — all
automatically. You don't need to master Flex to use Symfony; just know that it's the reason
installing packages feels lighter than plain Composer usage elsewhere.
Key Top-Level Folders
| Folder | What lives here |
|---|---|
config/ | Application configuration and route definitions |
src/ | Your application's PHP code — controllers, entities, services |
templates/ | Twig view files rendered by your controllers |
public/ | The web server's document root — the only folder exposed to the browser |
var/ | Generated cache and log files, safe to clear |
src/ and config/ are organized, and why.