docs/globals.txt

   1 globals.txt
   2
   3 Globals are evil. The original MediaWiki code relied on
   4 globals for processing context far too often. MediaWiki
   5 development since then has been a story of slowly moving
   6 context out of global variables and into objects. Storing
   7 processing context in object member variables allows those
   8 objects to be reused in a much more flexible way. Consider
   9 the elegance of:
  10
  11     # Generate the article HTML as if viewed by a web request
  12     $article = new Article( Title::newFromText( $t ) );
  13     $article->view();
  14
  15 versus
  16
  17     # Save current globals
  18     $oldTitle = $wgTitle;
  19     $oldArticle = $wgArticle;
  20
  21     # Generate the HTML
  22     $wgTitle = Title::newFromText( $t );
  23     $wgArticle = new Article;
  24     $wgArticle->view();
  25
  26     # Restore globals
  27     $wgTitle = $oldTitle
  28     $wgArticle = $oldArticle
  29
  30 Some of the current MediaWiki developers have an idle
  31 fantasy that some day, globals will be eliminated from
  32 MediaWiki entirely, replaced by an application object which
  33 would be passed to constructors. Whether that would be an
  34 efficient, convenient solution remains to be seen, but
  35 certainly PHP 5 makes such object-oriented programming
  36 models easier than they were in previous versions.
  37
  38 For the time being though, MediaWiki programmers will have
  39 to work in an environment with some global context. At the
  40 time of writing, 418 globals were initialised on startup by
  41 MediaWiki. 304 of these were configuration settings, which
  42 are documented in DefaultSettings.php. There is no
  43 comprehensive documentation for the remaining 114 globals,
  44 however some of the most important ones are listed below.
  45 They are typically initialised either in index.php or in
  46 Setup.php.
  47
  48 For a description of the classes, see design.txt.
  49
  50 $wgTitle
  51         Title object created from the request URL.
  52
  53 $wgArticle
  54         Article object corresponding to $wgTitle.
  55
  56 $wgOut
  57         OutputPage object for HTTP response.
  58
  59 $wgUser
  60         User object for the user associated with the current
  61         request.
  62
  63 $wgLang
  64         Language object selected by user preferences.
  65
  66 $wgContLang
  67         Language object associated with the wiki being
  68         viewed.
  69
  70 $wgParser
  71         Parser object. Parser extensions register their
  72         hooks here.
  73
  74 $wgRequest
  75         WebRequest object, to get request data
  76
  77 $wgMemc, $messageMemc, $parserMemc
  78         Object caches
  79
  80 $wgMessageCache
  81         Message cache, to manage interface messages
  82