I've been skimming the archives looking for something unrelated, and noticed that we fairly regularly have threads about compatibility, specifically the use of function X or feature Y in PHP, CSS, skins, or whatever. I concluded that we don't really have one centralised place where we document the software we support. So in the spirit of documentation, I've created another page to complement the other half dozen which already discuss system requirements (:-D) at mw.org: http://www.mediawiki.org/wiki/Compatibility which is distinct primarily in a) trying to record which versions *did* support software which we now say we don't support, and b) including browsers and css/js.
I wanted to bring it to everyone's attention primarily to check that we're all agreed on the software we no longer support. In addition to PHP4, PHP5.3.1 and MySQL3, which have been unsupported for donkey's years, I've marked PHP5.0 as unsupported (per [1][2]), since 1.15; that's a pretty arbitrary version to choose, but I picked one with some overlap with PHP 5.3. I've also marked IE <6 as unsupported, as IIRC someone said that recently (:-D). Is that accurate?
For the future, PHP5.1 has just seen in its fifth New Year. Dropping support there would allow us to use __tostring() magic on various objects, which could be useful in various places. Equally, the Wikimedia cluster has run MySQL 5 for over a year now [3], and it's approaching its eighth birthday; MySQL 4.0 and 4.1 are no longer maintained.
Of course, we're not saying "right, we don't support X, let's go add fun things to make absolutely sure that it doesn't work"; once a product is unsupported, we allow incompatibilities to gradually creep in in the course of normal development. We're not going to go change the recentchanges table to use BITs just because we can; but we might use that type if we introduce *new* columns.
Also interested in what people think about the CSS/JS/Text-only section. Is that a fair summary of our position?
--HM
[1] http://lists.wikimedia.org/pipermail/wikitech-l/2009-June/043584.html [2] http://lists.wikimedia.org/pipermail/wikitech-l/2010-October/049828.html [3] http://lists.wikimedia.org/pipermail/wikitech-l/2009-December/046127.html