How to Upgrade your Symfony Project

So a new Symfony release has come out and you want to upgrade, great! Fortunately,

because Symfony protects backwards-compatibility very closely, this *should*

be quite easy.

Upgrading a Patch Version (e.g. 2.6.0 to 2.6.1)

If you're upgrading and only the patch version (the last number) is changing,

then it's *really* easy:

.. code-block:: bash

That's it! You should not encounter any backwards-compatability breaks or

need to change anything else in your code.

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:

.. code-block:: bash

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-compability changes.

Upgrading a Minor Version (e.g. 2.5.3 to 2.6.0)

If you're upgrading a minor version (where the middle number changes), then

you should also *not* encounter significant backwards compability changes.

For details, see our :doc:`/contributing/code/bc`.

However, some backwards-compability breaks *are* possible, and you'll learn

in a second how to prepare for them.

There are two steps to upgrading:

1. :ref:`upgrade-minor-symfony-composer`;

2. :ref:`upgrade-minor-symfony-code`, which includes instructions for each version.

.. _`upgrade-minor-symfony-composer`:

Update the Symfony Library

First, you need to update Symfony by modifying your ``composer.json`` to

use the new version:

.. code-block:: json

Next, update the same as before:

.. code-block:: bash

Updating a minor version like this should *not* cause any dependency issues,

though it's always possible that an outside library or bundle you're using

didn't support this new version of Symfony at the version you have of that

library. In that case, consult the library: you may need to modify its version

in ``composer.json`` and run a full ``composer update``.

.. _`upgrade-minor-symfony-code`:

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, along with some other

details.

Upgrading to Symfony 2.6

First, of course, update your ``composer.json`` file with the ``2.6`` version

of Symfony as described above in :ref:`upgrade-minor-symfony-composer`.

Check the `UPGRADE-2.6`_ document for details. Highlights:

* If you're using PdoSessionStorage, there was a change in the session schema

that **requires** your session table to be updated. See :doc:`/cookbook/configuration/pdo_session_storage`.

* Symfony 2.6 comes with a great new `dump`_ function. To use it, you'll

need to add the new ``DebugBundle`` to your ``AppKernel``. See

`UPGRADE-2.6-DebugBundle`_ for details.

Upgrading to Symfony 2.5

First, of course, update your ``composer.json`` file with the ``2.5`` version

of Symfony as described above in :ref:`upgrade-minor-symfony-composer`.

Check the `UPGRADE-2.5`_ document for details. Highlights:

* This version introduced a new Validator API. But, as long as you're using

PHP 5.3.9 or higher, you can configure Symfony in a way that allows you

to use the new API, but still let the old API work (called ``2.5-bc``).

See the `UPGRADE-2.5-Validator`_ for details.

.. _`UPGRADE-2.5`: https://github.com/symfony/symfony/blob/2.5/UPGRADE-2.5.md

.. _`UPGRADE-2.5-Validator`: https://github.com/symfony/symfony/blob/2.7/UPGRADE-2.5.md#validator

.. _`UPGRADE-2.6`: https://github.com/symfony/symfony/blob/2.6/UPGRADE-2.6.md

.. _`UPGRADE-2.6-DebugBundle`: https://github.com/symfony/symfony/blob/2.6/UPGRADE-2.6.md#vardumper-and-debugbundle