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The Release Process
The Release Process¶
This document explains the process followed by the Symfony project to develop, release and maintain its different versions.
Symfony releases follow the semantic versioning strategy and they are published through a time-based model:
- A new Symfony patch version (e.g. 2.8.15, 4.1.7) comes out roughly every month. It only contains bug fixes, so you can safely upgrade your applications;
- A new Symfony minor version (e.g. 2.8, 3.2, 4.1) comes out every six months: one in May and one in November. It contains bug fixes and new features, but it doesn't include any breaking change, so you can safely upgrade your applications;
- A new Symfony major version (e.g. 3.0, 4.0) comes out every two years. It can contain breaking changes, so you may need to do some changes in your applications before upgrading.
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The full development period for any major or minor version lasts six months and is divided into two phases:
- Development: Four months to add new features and to enhance existing ones;
- Stabilization: Two months to fix bugs, prepare the release, and wait for the whole Symfony ecosystem (third-party libraries, bundles, and projects using Symfony) to catch up.
During the development phase, any new feature can be reverted if it won't be finished in time or if it won't be stable enough to be included in the current final release.
Check out the Symfony Roadmap to learn more about any specific version.
Starting from the Symfony 3.x branch, the number of minor versions is limited to five per branch (X.0, X.1, X.2, X.3 and X.4). The last minor version of a branch (e.g. 3.4, 4.4, 5.4) is considered a long-term support version and the other ones are considered standard versions:
|Version Type||Bugs are fixed for...||Security issues are fixed for...|
|Standard||8 months||14 months|
|Long-Term Support (LTS)||3 years||4 years|
After the active maintenance of a Symfony version has ended, you can get professional Symfony support from SensioLabs, the company which sponsors the Symfony project.
Our Backward Compatibility Promise is very strict and allows developers to upgrade with confidence from one minor version of Symfony to the next one.
When a feature implementation cannot be replaced with a better one without breaking backward compatibility, Symfony deprecates the old implementation and adds a new preferred one along side. Read the conventions document to learn more about how deprecations are handled in Symfony.
This deprecation policy also requires a custom development process for major versions (4.0, 5.0, 6.0, etc.) In those cases, Symfony develops at the same time two versions: the new major one (e.g. 4.0) and the latest version of the previous branch (e.g. 3.4).
Both versions have the same new features, but they differ in the deprecated features. The oldest version (3.4 in this example) contains all the deprecated features whereas the new version (4.0 in this example) removes all of them.
This allows you to upgrade your projects to the latest minor version (e.g. 3.4), see all the deprecation messages and fix them. Once you have fixed all those deprecations, you can upgrade to the new major version (e.g. 4.0) without effort, because it contains the same features (the only difference are the deprecated features, which your project no longer uses).
This release process was adopted to give more predictability and transparency. It was discussed based on the following goals:
- Shorten the release cycle (allow developers to benefit from the new features faster);
- Give more visibility to the developers using the framework and Open-Source projects using Symfony;
- Improve the experience of Symfony core contributors: everyone knows when a feature might be available in Symfony;
- Coordinate the Symfony timeline with popular PHP projects that work well with Symfony and with projects using Symfony;
- Give time to the Symfony ecosystem to catch up with the new versions (bundle authors, documentation writers, translators, ...);
- Give companies a strict and predictable timeline they can rely on to plan their own projects development.
The six month period was chosen as two releases fit in a year. It also allows for plenty of time to work on new features and it allows for non-ready features to be postponed to the next version without having to wait too long for the next cycle.
The dual maintenance mode was adopted to make every Symfony user happy. Fast movers, who want to work with the latest and the greatest, use the standard version: a new version is published every six months, and there is a two months period to upgrade. Companies wanting more stability use the LTS versions: a new version is published every two years and there is a year to upgrade.
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.