From time to time, PHP-Fusion issue upgrades to your sites software.
These upgrades will contain a file called "upgrade.php" which is to be placed in the administration folder.
The database needs to be altered, if not for structural changes it need to update your PHP-Fusion´s version number.
It's very important that you always run the upgrade script whenever one is released.
All new releases contains a readme with clear instructions on the procedure for that current upgrade.
For any questions, please visit our Upgrading issues Forum.