Upgrading Existing Applications to Symfony Flex

Using Symfony Flex is optional, even in Symfony 4, where Flex is used by default. However, Flex is so convenient and improves your productivity so much that it's strongly recommended to upgrade your existing applications to it.

Symfony Flex recommends that applications use the following directory structure, which is the same used by default in Symfony 4, but you can customize some directories:

├── assets/
├── bin/
│   └── console
├── config/
│   ├── bundles.php
│   ├── packages/
│   ├── routes.yaml
│   └── services.yaml
├── public/
│   └── index.php
├── src/
│   ├── ...
│   └── Kernel.php
├── templates/
├── tests/
├── translations/
├── var/
└── vendor/

This means that installing the symfony/flex dependency in your application is not enough. You must also upgrade the directory structure to the one shown above. There's no automatic tool to make this upgrade, so you must follow these manual steps:

  1. Install Flex as a dependency of your project:

    $ composer require symfony/flex
  2. If the project's composer.json file contains symfony/symfony dependency, it still depends on the Symfony Standard Edition, which is no longer available in Symfony 4. First, remove this dependency:

    $ composer remove symfony/symfony

    Now add the symfony/symfony package to the conflict section of the project's composer.json file as shown in this example of the skeleton-project so that it will not be installed again:

        "require": {
            "symfony/flex": "^1.0",
    +     },
    +     "conflict": {
    +         "symfony/symfony": "*"

    Now you must add in composer.json all the Symfony dependencies required by your project. A quick way to do that is to add all the components that were included in the previous symfony/symfony dependency and later you can remove anything you don't really need:

    $ composer require annotations asset orm-pack twig \
      logger mailer form security translation validator
    $ composer require --dev dotenv maker-bundle orm-fixtures profiler
  3. If the project's composer.json file doesn't contain the symfony/symfony dependency, it already defines its dependencies explicitly, as required by Flex. Reinstall all dependencies to force Flex to generate the configuration files in config/, which is the most tedious part of the upgrade process:

    $ rm -rf vendor/*
    $ composer install
  4. No matter which of the previous steps you followed. At this point, you'll have lots of new config files in config/. They contain the default config defined by Symfony, so you must check your original files in app/config/ and make the needed changes in the new files. Flex config doesn't use suffixes in config files, so the old app/config/config_dev.yml goes to config/packages/dev/*.yaml, etc.

  5. The most important config file is app/config/services.yml, which now is located at config/services.yaml. Copy the contents of the default services.yaml file and then add your own service configuration. Later you can revisit this file because thanks to Symfony's autowiring feature you can remove most of the service configuration.


    Make sure that your previous configuration files don't have imports declarations pointing to resources already loaded by Kernel::configureContainer() or Kernel::configureRoutes() methods.

  6. Move the rest of the app/ contents as follows (and after that, remove the app/ directory):

    • app/Resources/views/ -> templates/
    • app/Resources/translations/ -> translations/
    • app/Resources/<BundleName>/views/ -> templates/bundles/<BundleName>/
    • rest of app/Resources/ files -> src/Resources/
  7. Move the original PHP source code from src/AppBundle/*, except bundle specific files (like AppBundle.php and DependencyInjection/), to src/.

    In addition to moving the files, update the autoload and autoload-dev values of the composer.json file as shown in this example to use App\ and App\Tests\ as the application namespaces (advanced IDEs can do this automatically).

    If you used multiple bundles to organize your code, you must reorganize your code into src/. For example, if you had src/UserBundle/Controller/DefaultController.php and src/ProductBundle/Controller/DefaultController.php, you could move them to src/Controller/UserController.php and src/Controller/ProductController.php.

  8. Move the public assets, such as images or compiled CSS/JS files, from src/AppBundle/Resources/public/ to public/ (e.g. public/images/).

  9. Move the source of the assets (e.g. the SCSS files) to assets/ and use Webpack Encore to manage and compile them.

  10. SYMFONY_DEBUG and SYMFONY_ENV environment variables were replaced by APP_DEBUG and APP_ENV. Copy their values to the new vars and then remove the former ones.

  11. Create the new public/index.php front controller copying Symfony's index.php source and, if you made any customization in your web/app.php and web/app_dev.php files, copy those changes into the new file. You can now remove the old web/ dir.

  12. Update the bin/console script copying Symfony's bin/console source and changing anything according to your original console script.

  13. Remove src/AppBundle/.

  14. Move the original source code from src/{App,...}Bundle/ to src/ and update the namespaces of every PHP file to be App\... (advanced IDEs can do this automatically).

  15. Remove the bin/symfony_requirements script and if you need a replacement for it, use the new Symfony Requirements Checker.

  16. Update the .gitignore file to replace the existing var/logs/ entry by var/log/, which is the new name for the log directory.

Customizing Flex Paths

The Flex recipes make a few assumptions about your project's directory structure. Some of these assumptions can be customized by adding a key under the extra section of your composer.json file. For example, to tell Flex to copy any PHP classes into src/App instead of src:

    "...": "...",

    "extra": {
        "src-dir": "src/App"

The configurable paths are:

  • bin-dir: defaults to bin/
  • config-dir: defaults to config/
  • src-dir defaults to src/
  • var-dir defaults to var/
  • public-dir defaults to public/

If you customize these paths, some files copied from a recipe still may contain references to the original path. In other words: you may need to update some things manually after a recipe is installed.

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