MediaWiki is the WikiEngine used by the WikiPedia project, the SourceWatch project, WikiQuote, WikiBooks, WikiTravel, UncycloPedia, and others, including all wikis on WikiCities. It is the wiki engine that hosts the most public wiki pages.
In support of the DocumentMode/ThreadMode segregation required of WikiPedia, it supports WikiNamespaces. Typically, the main space is reserved for DocumentMode, with a "Talk:" namespace for ThreadMode content discussion. Many of the conventions developed here and on other wikis are implemented as separate namespaces on MediaWiki. There is a "User:" namespace for HomePages, a "Category:" namespace for categories, a "Template:" namespace for transcluded content, a "Special:" namespace for script-generated content and a "Help:" namespace for information for new users. Wikis may also implement their own namespaces: WikiPedia defines a "Wikipedia:" namespace for its own site-specific conventions and documentation and meta-discussion.
Code base was poor, but steadily improving. A lot of hacks are being phased out, and improved support for third party extensions makes adding functionality easier. Skin engine is still rather inconsistent and could do with rewriting (and all skins moving to one base class). Adds some flexible user permissions settings in 1.5 version, and is generally a lot friendlier to smaller wiki admins now.
I just installed it on a test system. It is easy to get working and quite flexible. Works right out of the box. I am a little miffed at how to customize and skin it, the docs on the main site are not that good IMHO. But it works and works well. Maybe that's why it's the top dog, for now.
Yes, the globals are troublesome, and the developers have made a good-faith effort to force PHP 4 to pass by reference by liberal application of ampersands, which makes debugging quite problematic. However it is easy to install and it has an attractive and intuitive interface.
Probably the author of this comment refers to the known limitation of PHP4 - passing a variable to a (sub)function does not handle the variable by "reference" (a "handle" is given over and all modifications on the variable inside the function really happen to the variable) but by creating a copy (which then is modified inside the function, but all might be lost, if the function does not return these "internals" to the calling function. Bypassing this behaviour is quite cumbersome in PHP 4. By the way: This "limitation" has been overcome in PHP 5.
Very easy to install using Wiki on a Stick (entire system <32MB) - http://www.mediawiki.org/wiki/Manual:Wiki_on_a_stick The package contains Apache+MySQL+PHP and MediaWiki. In my first try the system is up and running in under 10 minutes.
It looks like this is good wiki as long as it is used by wikipedia. Also it indexes well on google. [Al]
MediaWiki 1.5 has some interesting new features that improve collaboration. Top on my list is email notification of selected page changes. I've found it difficult to get people to check the wiki daily for important changes, but with email notifications, I only have to get them to check their email daily. :-) -- JanSteinman
It can't generate links using WikiNames! I thought that it was just disabled on Wikipedia where accurate titles are a requirement.