Proposing a Change

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Proposing a Change


Do you prefer video tutorials? Check out the Contributing Back To Symfony screencast series.

A pull request, "PR" for short, is the best way to provide a bug fix or to propose enhancements to Symfony.

Step 1: Check existing Issues and Pull Requests

Before working on a change, check to see if someone else also raised the topic or maybe even started working on a PR by searching on GitHub.

If you are unsure or if you have any questions during this entire process, please ask your questions on the #contribs channel on Symfony Slack.

Step 2: Setup your Environment

Install the Software Stack

Before working on Symfony, setup a friendly environment with the following software:

  • Git;
  • PHP version 7.2.5 or above.

Configure Git

Set up your user information with your real name and a working email address:

$ git config --global "Your Name"
$ git config --global


If you are new to Git, you are highly recommended to read the excellent and free ProGit book.


If your IDE creates configuration files inside the project's directory, you can use global .gitignore file (for all projects) or .git/info/exclude file (per project) to ignore them. See GitHub's documentation.


Windows users: when installing Git, the installer will ask what to do with line endings, and suggests replacing all LF with CRLF. This is the wrong setting if you wish to contribute to Symfony! Selecting the as-is method is your best choice, as Git will convert your line feeds to the ones in the repository. If you have already installed Git, you can check the value of this setting by typing:

$ git config core.autocrlf

This will return either "false", "input" or "true"; "true" and "false" being the wrong values. Change it to "input" by typing:

$ git config --global core.autocrlf input

Replace --global by --local if you want to set it only for the active repository

Get the Symfony Source Code

Get the Symfony source code:

  • Create a GitHub account and sign in;
  • Fork the Symfony repository (click on the "Fork" button);
  • After the "forking action" has completed, clone your fork locally (this will create a symfony directory):
$ git clone
  • Add the upstream repository as a remote:
$ cd symfony
$ git remote add upstream

Check that the current Tests Pass

Now that Symfony is installed, check that all unit tests pass for your environment as explained in the dedicated document.

Step 3: Work on your Pull Request

The License

Before you start, you should be aware that all the code you are going to submit must be released under the MIT license.

Choose the right Branch

Before working on a PR, you must determine on which branch you need to work:

  • If you are fixing a bug for an existing feature or want to make a change that falls into the list of acceptable changes in patch versions, pick the oldest concerned maintained branch (you can find them on the Symfony releases page). E.g. if you found a bug introduced in v5.1.10, you need to work on 5.4.
  • 6.2, if you are adding a new feature.

    The only exception is when a new major Symfony version (5.0, 6.0, etc.) comes out every two years. Because of the special development process of those versions, you need to use the previous minor version for the features (e.g. use 4.4 instead of 5.0, use 5.4 instead of 6.0, etc.)


All bug fixes merged into maintenance branches are also merged into more recent branches on a regular basis. For instance, if you submit a PR for the 4.4 branch, the PR will also be applied by the core team on the 5.x and 6.x branches.

Create a Topic Branch

Each time you want to work on a PR for a bug or on an enhancement, create a topic branch:

$ git checkout -b BRANCH_NAME 6.1

Or, if you want to provide a bug fix for the 4.4 branch, first track the remote 4.4 branch locally:

$ git checkout --track origin/4.4

Then create a new branch off the 4.4 branch to work on the bug fix:

$ git checkout -b BRANCH_NAME 4.4


Use a descriptive name for your branch (ticket_XXX where XXX is the ticket number is a good convention for bug fixes).

The above checkout commands automatically switch the code to the newly created branch (check the branch you are working on with git branch).

Use your Branch in an Existing Project

If you want to test your code in an existing project that uses symfony/symfony or Symfony components, you can use the link utility provided in the Git repository you cloned previously. This tool scans the vendor/ directory of your project, finds Symfony packages it uses, and replaces them by symbolic links to the ones in the Git repository.

$ php link /path/to/your/project

Before running the link command, be sure that the dependencies of the project you want to debug are installed by running composer install inside it.


If symlinks to your local Symfony fork cannot be resolved inside your project due to your dev environment (for instance when using Vagrant where only the current project directory is mounted), you can alternatively use the --copy option. When finishing testing your Symfony code into your project, you can use the --rollback option to make your project back to its original dependencies.

Work on your Pull Request

Work on the code as much as you want and commit as much as you want; but keep in mind the following:

  • Read about the Symfony conventions and follow the coding standards (use git diff --check to check for trailing spaces -- also read the tip below);
  • Add unit tests to prove that the bug is fixed or that the new feature actually works;
  • Try hard to not break backward compatibility (if you must do so, try to provide a compatibility layer to support the old way) -- PRs that break backward compatibility have less chance to be merged;
  • Do atomic and logically separate commits (use the power of git rebase to have a clean and logical history);
  • Never fix coding standards in some existing code as it makes the code review more difficult;
  • Write good commit messages: Start by a short subject line (the first line), followed by a blank line and a more detailed description.

    The subject line should start with the Component, Bridge or Bundle you are working on in square brackets ([DependencyInjection], [FrameworkBundle], ...).

    Then, capitalize the sentence, do not end with a period, and use an imperative verb to start.

    Here is a full example of a subject line: [MagicBundle] Add `MagicConfig` that allows configuring things.


When submitting pull requests, fabbot checks your code for common typos and verifies that you are using the PHP coding standards as defined in PSR-1 and PSR-2.

A status is posted below the pull request description with a summary of any problems it detects or any GitHub Actions build failures.

Prepare your Pull Request for Submission

When your PR is not about a bug fix (when you add a new feature or change an existing one for instance), it must also include the following:

  • An explanation of the changes in the relevant CHANGELOG file(s) (the [BC BREAK] or the [DEPRECATION] prefix must be used when relevant);
  • An explanation on how to upgrade an existing application in the relevant UPGRADE file(s) if the changes break backward compatibility or if you deprecate something that will ultimately break backward compatibility.

Step 4: Submit your Pull Request

Whenever you feel that your PR is ready for submission, follow the following steps.

Rebase your Pull Request

Before submitting your PR, update your branch (needed if it takes you a while to finish your changes):

$ git checkout 6.1
$ git fetch upstream
$ git merge upstream/6.1
$ git checkout BRANCH_NAME
$ git rebase 6.1


Replace 6.1 with the branch you selected previously (e.g. 4.4) if you are working on a bug fix.

When doing the rebase command, you might have to fix merge conflicts. git status will show you the unmerged files. Resolve all the conflicts, then continue the rebase:

$ git add ... # add resolved files
$ git rebase --continue

Check that all tests still pass and push your branch remotely:

$ git push --force origin BRANCH_NAME

Make a Pull Request

You can now make a pull request on the symfony/symfony GitHub repository.


Take care to point your pull request towards symfony:4.4 if you want the core team to pull a bug fix based on the 4.4 branch.

To ease the core team work, always include the modified components in your pull request message, like in:

[Yaml] fixed something
[Form] [Validator] [FrameworkBundle] added something

The default pull request description contains a table which you must fill in with the appropriate answers. This ensures that contributions may be reviewed without needless feedback loops and that your contributions can be included into Symfony as quickly as possible.

Some answers to the questions trigger some more requirements:

  • If you answer yes to "Bug fix?", check if the bug is already listed in the Symfony issues and reference it/them in "Fixed tickets";
  • If you answer yes to "New feature?", you must submit a pull request to the documentation and reference it under the "Doc PR" section;
  • If you answer yes to "BC breaks?", the PR must contain updates to the relevant CHANGELOG and UPGRADE files;
  • If you answer yes to "Deprecations?", the PR must contain updates to the relevant CHANGELOG and UPGRADE files;
  • If you answer no to "Tests pass", you must add an item to a todo-list with the actions that must be done to fix the tests;
  • If the "license" is not MIT, just don't submit the pull request as it won't be accepted anyway.

If some of the previous requirements are not met, create a todo-list and add relevant items:

- [ ] fix the tests as they have not been updated yet
- [ ] submit changes to the documentation
- [ ] document the BC breaks

If the code is not finished yet because you don't have time to finish it or because you want early feedback on your work, add an item to todo-list:

- [ ] finish the code
- [ ] gather feedback for my changes

As long as you have items in the todo-list, please prefix the pull request title with "[WIP]".

In the pull request description, give as much detail as possible about your changes (don't hesitate to give code examples to illustrate your points). If your pull request is about adding a new feature or modifying an existing one, explain the rationale for the changes. The pull request description helps the code review and it serves as a reference when the code is merged (the pull request description and all its associated comments are part of the merge commit message).

In addition to this "code" pull request, you must also send a pull request to the documentation repository to update the documentation when appropriate.

Step 5: Receiving Feedback

We ask all contributors to follow some best practices to ensure a constructive feedback process.

If you think someone fails to keep this advice in mind and you want another perspective, please join the #contribs channel on Symfony Slack. If you receive feedback you find abusive please contact the CARE team.

The core team is responsible for deciding which PR gets merged, so their feedback is the most relevant. So do not feel pressured to refactor your code immediately when someone provides feedback.

Automated Feedback

There are many automated scripts that will provide feedback on a pull request.


fabbot will review code style, check for common typos and make sure the git history looks good. If there are any issues, fabbot will often suggest what changes that should be done. Most of the time you get a command to run to automatically fix the changes.

It is rare, but fabbot could be wrong. One should verify if the suggested changes make sense and that they are related to the pull request.


Psalm will make a comment on a pull request if it discovers any potential type errors. The Psalm errors are not always correct, but each should be reviewed and discussed. A pull request should not update the Psalm baseline nor add @psalm- annotations.

After the Psalm phar is installed, the analysis can be run locally with:

$ psalm.phar src/Symfony/Component/Workflow

Automated Tests

A series of automated tests will run when submitting the pull request. These test the code under different conditions, to be sure nothing important is broken. Test failures can be unrelated to your changes. If you think this is the case, you can check if the target branch has the same errors and leave a comment on your PR.

Otherwise, the test failure might be caused by your changes. The following test scenarios run on each change:

PHPUnit / Tests

This job runs on Ubuntu using multiple PHP versions (each in their own job). These jobs run the testsuite just like you would do locally.

A failure in these jobs often indicates a bug in the code.

PHPUnit / Tests (high-deps)

This job checks each package (bridge, bundle or component) in src/ individually by calling composer update and phpunit from inside each package.

A failure in this job often indicates a missing package in the composer.json of the failing package (e.g. src/Symfony/Bundle/FrameworkBundle/composer.json).

This job also runs relevant packages using a "flipped" test (indicated by a ^ suffix in the package name). These tests checkout the previous major release (e.g. 4.4 for a pull requests on 5.4) and run the tests with your branch as dependency.

A failure in these flipped tests indicate a backwards compatibility break in your changes.

PHPUnit / Tests (low-deps)

This job also checks each package individually, but then uses composer update --prefer-lowest before running the tests.

A failure in this job often indicates a wrong version range or a missing package in the composer.json of the failing package.


This job runs on Windows using the x86 architecture and the lowest supported PHP version. All tests first run without extra PHP extensions. Then, all skipped tests are run using all required PHP extensions.

A failure in this job often indicate that your changes do not support Windows, x86 or PHP with minimal extensions.

Integration / Tests

Integration tests require other services (e.g. Redis or RabbitMQ) to run. This job only runs the tests in the integration PHPUnit group.

A failure in this job indicates a bug in the communication with these services.

PHPUnit / Tests (experimental)
This job always passes (even with failing tests) and is used by the core team to prepare for the upcoming PHP versions.

Rework your Pull Request

Based on the feedback on the pull request, you might need to rework your PR. Before re-submitting the PR, rebase with upstream/5.x or upstream/4.4, don't merge; and force the push to the origin:

$ git rebase -f upstream/6.1
$ git push --force origin BRANCH_NAME


When doing a push --force, always specify the branch name explicitly to avoid messing other branches in the repository (--force tells Git that you really want to mess with things so do it carefully).

Moderators earlier asked you to "squash" your commits. This means you will convert many commits to one commit. This is no longer necessary today, because Symfony project uses a proprietary tool which automatically squashes all commits before merging.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.