Inter Wiki
This wiki supports Inter Wiki links in a style copied from 
UseMod: wiki. Links to pages in other wikis can be made without having to know or type the full URLs, for example: MeatBall:InterWiki will link to the page named "~Inter Wiki" at Meatball wiki.
The ~Inter Wiki map is taken from the the <verbatim> block in Inter Wiki Map, but that page must be locked for it to work. This denies a potential hacker the ability to nefariously change every ~Inter Wiki link to point to some evil URL. If no map is found in Inter Wiki Map (or the page is not locked), Php Wiki will fall back to using the file lib/interwiki.map in your phpwiki distribution. The ~Inter Wiki map file in use at Php Wiki: can be viewed at 
http://phpwiki.sf.net/interwiki.map.
The map file is manually updated. It is based upon and periodically synchronized with UseMod's InterMap but it is not quite identical. One notable difference from UseMod: is that Php Wiki supports '%s' within the URLs in the map--see the entry for RFC for an example of how this works.
Not all of the entries in the Inter Wiki Map are actual wikis. For example, these are just regular web sites: Dictionary:fungible, JargonFile:Alderson loop, IMDB:Roman Holiday, RFC:2822, and ISBN:020171499X.
The "Category" moniker is a special entry which allows one to link a wiki page to a Category page without creating a back-reference. Thus Category:Category links to the ?Category Category page, yet this page won't show up in the back-links listing of ?Category Category.
The term "Inter Wiki" also refers to a broader concept. See PhpWiki:InterWikiSearch for more links.