Many problems can be resolved by clearing Symfony’s cache.
Basically, you need to be able to run the symfony command line application, which is located in the root directory of this project.
php symfony cache:clear
Additionally, if apc.stat is not activated
in your PHP configuration, you’ll also have to clear the opcode cache
apc_clear_cache('opcode') from a script or reloading PHP-FPM:
sudo /etc/init.d/php5-fpm reload