Thread:Project:Support desk/MediaWiki 1.5 to 1.21 upgrade/reply (3)

If your old wiki continues to work properly on the new server depends: What PHP and MySQL versions does MediaWiki 1.5 support? And what versions do you have on the newest server?

Basically I would first copy it to the new server and then do an update just as usual. Upgrading instructions are available here Manual:Upgrade.