如何配置php RAR归档安装程序窗口

<?php $rar_arch = RarArchive::open('filename.rar'); if ($rar_arch === FALSE)
die("Failed opening file");
$entries = $rar_arch->getEntries(); if ($entries === FALSE)
die("Failed fetching entries");
echo "Found " . count($entries) . " extract'location";
if (empty($entries))
die("No valid entries found.");
$stream = reset($entries)->getStream();
if ($stream === FALSE)
die("Failed opening first file");
$rar_arch->close();
echo "Content of first one follows:'n";
echo stream_get_contents($stream);
fclose($stream); ?> 

http://php.net/manual/en/rar.installation.php

错误是:

Fatal error: Class 'RarArchive' not found in C:'Zend'Apache2'htdocs'CSV'example.php on line 2

extension=php_rar.dll