[Summary view] [Print] [Text view]

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