There are many breaking changes: https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/v3.0.0/UPGRADE-v3.md See also https://github.com/FriendsOfPHP/PHP-CS-Fixer/releases/tag/v3.0.0
