You can read upgrade readme file in symfony repository to see changes that can touch your code.
I am update one project from 2.1 to 2.3 and it was really painless. Update from 2.0 to 2.1 was very painful. Mostly it depends on vendor bundles, which will want to update to new versions.
Update
To update your application you must change you composer.json
file. There is a composer.json file from symfony-standard repository. You must change version in your composer.json
file and run php composer.phar update
. Example to update symfony core change "symfony/symfony": "2.1.*"
, to "symfony/symfony": "2.3.*"
. But be careful, there are bundles depending between versions on each other. Example doctrine-bundle v1.1
only works with symfony 2.1
Update(some of founded deprecates)
trust_proxy_headers option is deprecated. See here.
MinLength and MaxLength validators is deprecated.
Min and Max validators is deprecated.
Field form type removed.
Some old twig blocks like {% block field_row %}
, {% block field_label %}
also removed(located in form_div_layout.html.twig
).
Symfony upgrade files(just for convenience)
Small hint
To find the correct version is useful to use https://packagist.org. Example on doctrine-bundle page, you can see which version suitable for 2.3 version.