Manual:$wgRequest

Overview
is used as a global singleton that contains an instance of the class. The WebRequest class encapsulates getting at data passed in the URL or via a POSTed form, handling removal of "magic quotes" slashes, stripping illegal input characters and normalizing Unicode sequences. See the class documentation and  for more details.

Examples
This code can be useful within hook functions when you want to return without executing additional function code if the user is editing, rather than viewing, the current page.

Deprecation
As with other globals, the use of  should be avoided when alternative methods are available. For example, when writing a special page, use the  method provided by the SpecialPage class, e.g.:

Hook functions
When you work with various hooks you can usually get the WebRequest object from the context, for example:

Special pages
In a special page context, one can use.

API modules
In an API module context, one can use.