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[lhc/web/wiklou.git] / docs / globals.txt

diff --git a/docs/globals.txt b/docs/globals.txt
index ac1a609..847fbed 100644 (file)
--- a/docs/globals.txt
+++ b/docs/globals.txt
@@ -1,29 +1,65 @@
-GLOBALS.DOC
-
-PHP loves globals. I hate them. This is not a great
-combination, but I manage. I could get rid of most of
-them by having a single "HTTP request" object, and using
-it to hold everything that's now global (which is exactly
-what I'd do in a Java servlet). But that's really
-awkward in PHP, and wouldn't really provide much benefit
-in readability or maintainability, so I go with the flow
-of PHP and use globals.  Here's documentation on the
-important globals used by the system.
+globals.txt
 
-$wgOut
-       OutputPage object for HTTP response.
+Globals are evil. The original MediaWiki code relied on globals for processing
+context far too often. MediaWiki development since then has been a story of
+slowly moving context out of global variables and into objects. Storing
+processing context in object member variables allows those objects to be reused
+in a much more flexible way. Consider the elegance of:
+
+    # Generate the article HTML as if viewed by a web request
+    $article = new Article( Title::newFromText( $t ) );
+    $article->view();
+
+versus
+
+    # Save current globals
+    $oldTitle = $wgTitle;
+    $oldArticle = $wgArticle;
+
+    # Generate the HTML
+    $wgTitle = Title::newFromText( $t );
+    $wgArticle = new Article;
+    $wgArticle->view();
+
+    # Restore globals
+    $wgTitle = $oldTitle
+    $wgArticle = $oldArticle
+
+Some of the current MediaWiki developers have an idle fantasy that some day,
+globals will be eliminated from MediaWiki entirely, replaced by an application
+object which would be passed to constructors. Whether that would be an
+efficient, convenient solution remains to be seen, but certainly PHP 5 makes
+such object-oriented programming models easier than they were in previous
+versions.
+
+For the time being though, MediaWiki programmers will have to work in an
+environment with some global context. At the time of writing, 418 globals were
+initialised on startup by MediaWiki. 304 of these were configuration settings,
+which are documented in DefaultSettings.php. There is no comprehensive
+documentation for the remaining 114 globals, however some of the most important
+ones are listed below. They are typically initialised either in index.php or in
+Setup.php.
 
 $wgTitle
        Title object created from the request URL.
 
+$wgOut
+       OutputPage object for HTTP response.
+
+$wgUser
+       User object for the user associated with the current request.
+
 $wgLang
-       Language object for this request.
+       Language object selected by user preferences.
 
-$wgArticle
-       Article object corresponsing to $wgTitle.
+$wgContLang
+       Language object associated with the wiki being viewed.
 
-$wgLinkCache
-       LinkCache object.
+$wgParser
+       Parser object. Parser extensions register their hooks here.
 
-...
+$wgRequest
+       WebRequest object, to get request data
 
+$wgMemc, $messageMemc
+       Object caches