Thread:Project:Support desk/Updateing old MediaWiki fails on DBUpdate Fatal error: Class 'MysqlUpdater'/reply (2)

> Class 'MysqlUpdater' not found in includes/installer/DatabaseUpdater.php on line 120

Are you sure you have copied all files of the new MediaWiki version into that installation? Also make sure that no old files are left. I once had a similar problem and I figured out that it was some profiling code, which I had used since ages, but that was no longer compatible with the new version.

Do you use a PHP code cache (like eAccelerator) on the server? If so, try emptying its cache.