Warning: require_once(Zend/Feed/Pubsubhubbub/CallbackInterface.php): failed to open stream: No such file or directory in C:\Apache24\htdocs\library\Zend\Feed\Pubsubhubbub\CallbackAbstract.php on line 26

Fatal error: require_once(): Failed opening required 'Zend/Feed/Pubsubhubbub/CallbackInterface.php' (include_path='.;C:\php\pear') in C:\Apache24\htdocs\library\Zend\Feed\Pubsubhubbub\CallbackAbstract.php on line 26