Dans un premier temps il faut que Composer soit installé sur votre système.

Ensuite rendez-vous dans le répértoire contenant votre composer.phar et executez:

php composer.phar create-project symfony/website-skeleton mon-projet

Là composer installe le projet dans le répértoire mon-projet.

Si il donne des erreurs, réglez les. C'est souvent un manque d'extension PHP.

Résultat:

Installing symfony/website-skeleton (v4.1.6.2)
  - Installing symfony/website-skeleton (v4.1.6.2): Loading from cache
Created project in protic-sadmin
Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Package operations: 94 installs, 0 updates, 0 removals
  - Installing ocramius/package-versions (1.3.0): Downloading (100%)
  - Installing symfony/flex (v1.1.1): Downloading (100%)

Prefetching 91 packages 🎶 💨
  - Downloading (100%)

  - Installing symfony/polyfill-mbstring (v1.9.0): Loading from cache
  - Installing doctrine/lexer (v1.0.1): Loading from cache
  - Installing doctrine/annotations (v1.6.0): Loading from cache
  - Installing doctrine/reflection (v1.0.0): Loading from cache
  - Installing doctrine/event-manager (v1.0.0): Loading from cache
  - Installing doctrine/collections (v1.5.0): Loading from cache
  - Installing doctrine/cache (v1.8.0): Loading from cache
  - Installing doctrine/persistence (v1.0.1): Loading from cache
  - Installing doctrine/inflector (v1.3.0): Loading from cache
  - Installing doctrine/common (v2.9.0): Loading from cache
  - Installing symfony/doctrine-bridge (v4.1.6): Loading from cache
  - Installing doctrine/doctrine-cache-bundle (1.3.3): Loading from cache
  - Installing doctrine/instantiator (1.1.0): Loading from cache
  - Installing symfony/console (v4.1.6): Loading from cache
  - Installing zendframework/zend-eventmanager (3.2.1): Loading from cache
  - Installing zendframework/zend-code (3.3.1): Loading from cache
  - Installing ocramius/proxy-manager (2.1.1): Loading from cache
  - Installing doctrine/dbal (v2.8.0): Loading from cache
  - Installing doctrine/migrations (v1.8.1): Loading from cache
  - Installing egulias/email-validator (2.1.6): Loading from cache
  - Installing jdorn/sql-formatter (v1.2.17): Loading from cache
  - Installing phpdocumentor/reflection-common (1.0.1): Loading from cache
  - Installing phpdocumentor/type-resolver (0.4.0): Loading from cache
  - Installing psr/cache (1.0.1): Loading from cache
  - Installing psr/container (1.0.0): Loading from cache
  - Installing psr/simple-cache (1.0.1): Loading from cache
  - Installing symfony/http-foundation (v4.1.6): Loading from cache
  - Installing symfony/event-dispatcher (v4.1.6): Loading from cache
  - Installing psr/log (1.0.2): Loading from cache
  - Installing symfony/debug (v4.1.6): Loading from cache
  - Installing symfony/http-kernel (v4.1.6): Loading from cache
  - Installing symfony/routing (v4.1.6): Loading from cache
  - Installing symfony/finder (v4.1.6): Loading from cache
  - Installing symfony/filesystem (v4.1.6): Loading from cache
  - Installing symfony/dependency-injection (v4.1.6): Loading from cache
  - Installing symfony/config (v4.1.6): Loading from cache
  - Installing symfony/cache (v4.1.6): Loading from cache
  - Installing symfony/framework-bundle (v4.1.6): Loading from cache
  - Installing sensio/framework-extra-bundle (v5.2.1): Loading from cache
  - Installing symfony/asset (v4.1.6): Loading from cache
  - Installing symfony/expression-language (v4.1.6): Loading from cache
  - Installing symfony/inflector (v4.1.6): Loading from cache
  - Installing symfony/property-access (v4.1.6): Loading from cache
  - Installing symfony/options-resolver (v4.1.6): Loading from cache
  - Installing symfony/intl (v4.1.6): Loading from cache
  - Installing symfony/polyfill-intl-icu (v1.9.0): Loading from cache
  - Installing symfony/form (v4.1.6): Loading from cache
  - Installing monolog/monolog (1.23.0): Loading from cache
  - Installing symfony/monolog-bridge (v4.1.6): Loading from cache
  - Installing doctrine/orm (v2.6.2): Loading from cache
  - Installing doctrine/doctrine-bundle (1.9.1): Loading from cache
  - Installing doctrine/doctrine-migrations-bundle (v1.3.1): Loading from cache
  - Installing symfony/orm-pack (v1.0.5): Loading from cache
  - Installing symfony/security (v4.1.6): Loading from cache
  - Installing symfony/security-bundle (v4.1.6): Loading from cache
  - Installing symfony/serializer (v4.1.6): Loading from cache
  - Installing symfony/property-info (v4.1.6): Loading from cache
  - Installing webmozart/assert (1.3.0): Loading from cache
  - Installing phpdocumentor/reflection-docblock (4.3.0): Loading from cache
  - Installing symfony/serializer-pack (v1.0.1): Loading from cache
  - Installing swiftmailer/swiftmailer (v6.1.3): Loading from cache
  - Installing symfony/swiftmailer-bundle (v3.2.3): Loading from cache
  - Installing symfony/translation (v4.1.6): Loading from cache
  - Installing symfony/validator (v4.1.6): Loading from cache
  - Installing psr/link (1.0.0): Loading from cache
  - Installing fig/link-util (1.0.0): Loading from cache
  - Installing symfony/web-link (v4.1.6): Loading from cache
  - Installing symfony/yaml (v4.1.6): Loading from cache
  - Installing symfony/process (v4.1.6): Loading from cache
  - Installing facebook/webdriver (1.6.0): Loading from cache
  - Installing symfony/polyfill-php72 (v1.9.0): Loading from cache
  - Installing symfony/var-dumper (v4.1.6): Loading from cache
  - Installing twig/twig (v2.5.0): Loading from cache
  - Installing symfony/twig-bridge (v4.1.6): Loading from cache
  - Installing symfony/web-profiler-bundle (v4.1.6): Loading from cache
  - Installing symfony/twig-bundle (v4.1.6): Loading from cache
  - Installing symfony/stopwatch (v4.1.6): Loading from cache
  - Installing symfony/profiler-pack (v1.0.3): Loading from cache
  - Installing symfony/monolog-bundle (v3.3.0): Loading from cache
  - Installing symfony/debug-bundle (v4.1.6): Loading from cache
  - Installing easycorp/easy-log-handler (v1.0.7): Loading from cache
  - Installing symfony/debug-pack (v1.0.6): Loading from cache
  - Installing symfony/dom-crawler (v4.1.6): Loading from cache
  - Installing symfony/dotenv (v4.1.6): Loading from cache
  - Installing nikic/php-parser (v4.1.0): Loading from cache
  - Installing symfony/maker-bundle (v1.7.0): Loading from cache
  - Installing symfony/phpunit-bridge (v4.1.6): Loading from cache
  - Installing symfony/browser-kit (v4.1.6): Loading from cache
  - Installing symfony/panther (v0.2.0): Loading from cache
  - Installing symfony/css-selector (v4.1.6): Loading from cache
  - Installing symfony/test-pack (v1.0.4): Loading from cache
  - Installing symfony/web-server-bundle (v4.1.6): Loading from cache
Generating autoload files
ocramius/package-versions:  Generating version class...
ocramius/package-versions: ...done generating version class
Symfony operations: 21 recipes (15f6d846c418b919b22fc7bc3a311bb3)
  - Configuring symfony/flex (>=1.0): From github.com/symfony/recipes:master
  - Configuring symfony/framework-bundle (>=3.3): From github.com/symfony/recipes:master
  - Configuring doctrine/annotations (>=1.0): From github.com/symfony/recipes:master
  - Configuring doctrine/doctrine-cache-bundle (>=1.3.3): From auto-generated recipe
  - Configuring symfony/console (>=3.3): From github.com/symfony/recipes:master
  - Configuring symfony/routing (>=4.0): From github.com/symfony/recipes:master
  - Configuring sensio/framework-extra-bundle (>=5.2): From github.com/symfony/recipes:master
  - Configuring doctrine/doctrine-bundle (>=1.6): From github.com/symfony/recipes:master
  - Configuring doctrine/doctrine-migrations-bundle (>=1.2): From github.com/symfony/recipes:master
  - Configuring symfony/security-bundle (>=3.3): From github.com/symfony/recipes:master
  - Configuring symfony/swiftmailer-bundle (>=2.5): From github.com/symfony/recipes:master
  - Configuring symfony/translation (>=3.3): From github.com/symfony/recipes:master
  - Configuring symfony/validator (>=4.1): From github.com/symfony/recipes:master
  - Configuring symfony/web-profiler-bundle (>=3.3): From github.com/symfony/recipes:master
  - Configuring symfony/twig-bundle (>=3.3): From github.com/symfony/recipes:master
  - Configuring symfony/monolog-bundle (>=3.1): From github.com/symfony/recipes:master
  - Configuring symfony/debug-bundle (>=4.1): From github.com/symfony/recipes:master
  - Configuring easycorp/easy-log-handler (>=1.0): From github.com/symfony/recipes:master
  - Configuring symfony/maker-bundle (>=1.0): From github.com/symfony/recipes:master
  - Configuring symfony/phpunit-bridge (>=4.1): From github.com/symfony/recipes:master
  - Configuring symfony/web-server-bundle (>=3.3): From github.com/symfony/recipes:master
Executing script cache:clear [OK]
Executing script assets:install public [OK]

Some files may have been created or updated to configure your new packages.
Please review, edit and commit them: these files are yours.


 What's next?


  * Run your application:
    1. Change to the project directory
    2. Create your code repository with the git init command
    3. Execute the php -S 127.0.0.1:8000 -t public command
    4. Browse to the http://localhost:8000/ URL.

       Quit the server with CTRL-C.
       Run composer require server --dev for a better web server.

  * Read the documentation at https://symfony.com/doc


 Database Configuration


  * Modify your DATABASE_URL config in .env

  * Configure the driver (mysql) and
    server_version (5.7) in config/packages/doctrine.yaml


 How to test?


  * Write test cases in the tests/ folder
  * Run php bin/phpunit

Dans votre navigateur ouvrir la page http://%VotreServeurWeb%/html/truc/machin/public/ et vous devriez voir cela:

Maintenant pour naviguer dans votre futur site utilisez l'URL http://%VotreServeurWeb%/html/truc/machin/public/index.php/MaRoute

La partie MaRoute de l'URL sera votre route dans le routing de Symfony