Skin-by-URL 2 is a MediaWiki extension that will cause the skin used
to display a page to be determined by the PHP script name in the Wiki
URL.  For example, MediaWiki URLs normally use the script name
"index.php" before the page-title portion of the URL.  This extension
examines request URLs for a script name other than "index", and if
present, sets the output skin to one whose name matches the requested
script name (if available).

When a skin is set via this extension, intra-wiki page-viewing URLs in
the generated page are modified so that they incorpoate the correct
script name to maintain continuity of the skin used as links are
followed.  To make a link from one wiki page to another force a return
to the normal handling of skins (site-wide default skin selection and
per-user custom skin selection), use external-link syntax for the URL
(e.g., "[url]" instead of "[[PageName]]") and specify the "normal" URL
for the desired page explicitly.

Intra-wiki links for purposes other than viewing pages (edit and
history links, etc.) are not modified and continue to use /index.php
URLs.  In addition, if a URL including the skin name is used for a
non-viewing "action", it will still not have the skin-selecting
effect, and MediaWiki's original skin-selection mechanism will
operate.

This extension is licensed under the AGPLv3.  It is a functional clone
of the obsolete, GPL-licensed MediaWiki extension SkinByURL
(http://www.mediawiki.org/wiki/Extension:SkinByURL) by Eric Myers, but
shares none of the original's code.



INSTALLATION

Place the skin-by-url-2 files in a directory of the same name under
"extensions" in your MediaWiki installation, and add the following to
your LocalSettings.php:

  $wgParserCacheType = CACHE_NONE;
  require_once( "$IP/extensions/skin-by-url-2/skin-by-url-2.php" );

In order for this extension to work, in addition to installing the
extension, administrators must create links (tested) or URL aliases
(will probably also work) from their desired skin-specific script
names to the default one (e.g., from "simple.php" to "index.php").
Yes, this is a little kludgey and adds an extra step to restoring a
completely destroyed wiki installation, but it is easy to understand
and manage.  Note that the names of the links used in place of
"index.php" must still end in ".php" to be recognized (or in whatever
value you've set for $wgScriptExtension).

This extension does not modify MediaWiki's internal notion of "the"
name of the wiki's entry-point script (e.g., it remains "index.php").
Because of this, and the fact that MediaWiki looks for the script name
to find the beginning of article titles when using "pretty URLs", you
*must* use the explicit-title form of URLs for your wiki:

  /wiki/index.php?title=My_Wiki_Article

for this extension to work, rather than the "pretty" URL format like

  /wiki/index.php/My_Wiki_Article

To accomplish this, also include:

  $wgUsePathInfo = false;

in your LocalSettings.php file.  *OR* if you'd like to use pretty URLs
for pages in your wiki when they're accessed via index.php, even
though you'll still have to use "title=" URLs for those that are to
set the skin, place the line

  $wgUsePathInfo = true;

in your LocalSettings.php file as you normally would to enable this
behavior, but make sure it comes *before* the 'require_once()' for
this extension.  Skin-by-URL 2 is smart enough to turn pretty URLs off
in those instances where a script name other than "index.php" is
detected.

MediaWiki doesn't provide an extension "hook" that would allow
Skin-by-URL 2 to support pretty-URL format without modification to a
core MediaWiki source file.  However, there is a simple fix if you are
willing to modify the MediaWiki source in your installation, described
next under "USING WITH 'PRETTY' URLs".



USING WITH 'PRETTY' URLs

While strongly recommended against, and a great complicating factor
for future software upgrades, it is possible for you to modify the
content of the "core" MediaWiki PHP files in order to change
MediaWiki's behavior.  If you want to use this extension along with
"pretty" URLs (ones that don't require the "title=" in them, enabled
by setting '$wgUsePathInfo=true;' in LocalSettings.php), you will have
to make such a modification.  (And then re-modify each time you
upgrade your MediaWiki software in the future.)

The change must be made in the 'interpolateTitle()' function in the
file:

  includes/WebRequest.php

In this function is a series of calls to the other function
'extractTitle()', all but the first of which is contained in an "if"
statement that starts out 'if( !matches &&'.  Insert the following
statements above the first of these 'if( !matches &&' blocks.

  global $wg_SBU2_skinNameFromUrl;
  if( !$matches && ($wg_SBU2_skinNameFromUrl != "") ) {
    $script = "/wiki/{$wg_SBU2_skinNameFromUrl}.php/$1";
    $matches = $this->extractTitle( $path, $script );
  }

This new code allows MediaWiki to extract article titles from pretty
URLs that use a skin-selecting script name instead of the default
one.  Note that, if your wiki uses a $wgScriptPath other than the
default "/wiki", you should change the preceding code to match.


STATUS

The implementation of skin-by-url-2 is currently quite immature.  It
has been tested with MediaWiki v1.15.1 only, and on Ubuntu
Debian/GNU/Linux only.  Also, this is my first effort in PHP (not to
mention my first MediaWiki extension), so any changes to make the PHP
code more idiomatic or the extension more in line with MediaWiki norms
are more than welcome.

Currently, this extension makes skin selections based on the script
name in the URL only.  Other available extensions provide (at least)
essentially the same behavior based on wiki namespace or article
category, see:

  http://www.mediawiki.org/wiki/Extension:SkinPerNamespace
  http://www.mediawiki.org/wiki/Extension:AdvancedSkinSystem

If your application needs to select the correct skin based on another
portion of the URL (a component of the query string, or of the host
name), I'd welcome changes to this extension implementing that with
appropriate configuration options.

There are several configuration options that could be added which I
have not.  For example, if you would like all intra-wiki URLs to use
the skin-selecting script name, you could set $wgScript to match the
script name in the incoming URL instead of connecting to the
GetLocalURL hook.

However, just changing the URLs is not sufficient to get MediaWiki to
use the URL-specified skin to be applied to all page types.  This can
be accomplished by changing Skin-by-URL 2's skin-selecting callback
from the OutputPageParserOutput hook to a hook called earlier in the
process and/or to multiple hooks.  Your mileage may vary.  However,
I'd welcome any changes like these as long as they're controlled by
configuration options so that the original behavior can still be
obtained.

The parser cache must be disabled for this extension in order to
prevent internal URLs that don't match the current skin selection from
being served.  Any change that would disable caching (both fetching
from and storing in) for requests using skin-selecting URLs but not
globally would be appreciated.