I've been running the wmf series of MW since late into 1.27. I've gone through all the 1.28/1.29 wmf updates up to 1.30.0-wmf.4 and never really had an issue with them. Yesterday I up'd to 1.30.0.wmf.5 from .4 and it appears the Category namespace died as I now receive http 500 errors on each Category page. All the other namespaces seem to be working as normal.
I found this error when tailing my MW log file.
[fatal] [ab557217] PHP Fatal Error: Access level to CategoryTreeCategoryPage::$mCategoryViewerClass must be public (as in class CategoryPage) [session] Saving all sessions on shutdown
Reverting back to 1.30.0.wmf.4 re-initiates the Category namespace.
Version .4 Works Version 1.30.0-wmf.4 your root ../includes/page/CategoryPage.php LINE 30: protected $mCategoryViewerClass = 'CategoryViewer';
Version .5 Fails. Version 1.30.0-wmf.5 your root ../includes/page/CategoryPage.php LINE 30: public $mCategoryViewerClass = 'CategoryViewer';
Editing CategoryPage.php in version 1.30.0-wmf.5 to *protected* instead of *public* resolves the http 500 error on Category pages.
I have no clue as to whether or not that is a correct fix but it fixed my lost Category problem.
Chap @ jonesipedia.com