Manual:WebRequest.php

WebRequest
The WebRequest class which encapsulates getting at data passed in the URL or via a POSTed form, handling remove of "magic quotes" slashes, stripping illegal input characters and normalizing Unicode sequences. A global instance of this class is available in $wgRequest. You should not create additional instances of this class, instead, use FauxRequest.

Functions
... many more, this is a partial list.
 * function getVal: get a scalar or null if the parameter was not passed
 * function getInt: same as before, but the value returned is an integer
 * function getBool: same as getVal, but returns a boolean value
 * function getArray: get an array or null if the parameter was not passed. If the parameter is a scalar, it will return an array with a single element.
 * function getCheck: return a boolean whether the parameter was passed, this is useful for checkboxes.
 * function getCookie: get a cookie from the $_COOKIE jar
 * function wasPosted: returns a bool whether the request was posted

FauxRequest
FauxRequest is a class extending WebRequest. Its purpose is to emulate a request with the values passed to the constructor.