Thread:Project:Support desk/MediaWiki Upgrade from 1.16 to 1.22.2/reply

1.16 is no longer supported, and we strongly encourage people to upgrade to 1.22.2 as 1.16 no longer gets security fixes.

There should be no issue with migrating to a 64bit server. If the server has a different domain or url scheme, you might have to change a couple variables in LocalSettings.php if they reference the domain of the server. Otherwise there shouldn't be any problems. If you are using UCA category collations ($wgCategoryCollation), changing versions of PHP can cause problems, however that feature is off by default.