[Mediawiki-l] Export by Category Extension

[kent sin]

I follow the instruction
(http://indifference.dyndns.org/savage/index.php?title=Export%20by%20category%20script&action=purge)
 to install the Export by category extension in 1.5.6

When add the line

$wgSpecialPages['APExport'] = new SpecialPage( 'APExport' );


Fatal error: Class 'SpecialPage' not found in C:\Program Files\Apache
Group\Apache2\htdocs\af\LocalSettings.php on line 115

How can I install it?

Are there any alternative way to export all the contents (or by
category) from mediawiki? I love to backup and transfer pages using
export other than database dump. I fell this is better way to kept a
safe copy as well as doing find/replace editing.

Thank you.

-- 
Sin Hang Kin.