Thread:Project:Support desk/ Fatal error:Call to undefined function wfGetMainCache() ExtensionLoader.php

mediawiki: Version 1.20 php: Version 5.4.7 mysql: Version 5.0.10 windows xp

Fatal error: Call to undefined function wfGetMainCache in C:\xampp\htdocs\mediawiki\extensions\ExtensionManager\ExtensionLoader.php on line 30

Can anyone help me?