Fengoffice installation with fatal error "Class 'DB' not found"

When you do a server migration, some fatal error appearing in fengoffice installation like:

[error] [client 127.0.0.1] PHP Fatal error:  Class 'DB' not found in C:\\wamp\\www\\feng\\init.php on line 111

You would try to delete the contents of the cache folder, it may contains hardcoded paths of your other server.