DokuWiki
From Sudelwiki
DokuWiki is a great WikiSystem that NEEDS NO DATABASE.
Yes, right - no MySQL hassle and no hoff on DB-Performance.
Why is that important to me?
Because - i want one million wiki pages and more on a normal cheapo webspace - and that is not possible with the otherwise great Mediawiki-Software.
DokuWiki API
DokuWiki seems to have an API - yeah!
And even some PHP examples on how to use that API - so - that's one more point for DokuWiki.