How to Upgrade Your Symfony Project

1) Update the Symfony Library via Composer¶

First, you need to update Symfony by modifying your composer.json file to use the new version:

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

    "require": {
        "php": ">=5.3.3",
        "symfony/symfony": "2.6.*",
        "...": "... no changes to anything else..."
    },
    "...": "...",
}

Next, use Composer to download new versions of the libraries:

$ composer update symfony/symfony

You may also want to upgrade the rest of your libraries. If you’ve done a good job with your version constraints in composer.json, you can do this safely by running:

$ composer update

But beware. If you have some bad version constraints in your composer.json, (e.g. dev-master), then this could upgrade some non-Symfony libraries to new versions that contain backwards-compatibility breaking changes.

2) Updating Your Code to Work with the new Version¶

In theory, you should be done! However, you may need to make a few changes to your code to get everything working. Additionally, some features you’re using might still work, but might now be deprecated. That’s actually ok, but if you know about these deprecations, you can start to fix them over time.

Every version of Symfony comes with an UPGRADE file that describes these changes. Below are links to the file for each version, which you’ll need to read to see if you need any code changes.