IE bug for a PHP script

I’m using this code to rotate a group of static images as headers on all pages except for the home page (on which a flash animation plays) It works fine…except in IE.

IE plays the flash animation on the home page, but does not want to recognoze the php that rotates the images..
The code is kind of old..I got it off a blog post dated 2003.
Any insight is appreciated

https://www.newseminary.org/staging/berke14q_wrdp/

<?php
/*
By Matt Mullenweg > https://photomatt.net
Inspired by Dan Benjamin > https://hiveware.com/imagerotator.php
Latest version always at:

https://photomatt.net/scripts/randomimage

*/// Make this the relative path to the images, like "../img" or "random/images/".
// If the images are in the same directory, leave it blank.
$folder = '';

// Space seperated list of extensions, you probably won't have to change this.
$exts = 'jpg jpeg png gif';

$files = array(); $i = -1; // Initialize some variables
if ('' == $folder) $folder = './';

$handle = opendir($folder);
$exts = explode(' ', $exts);
while (false !== ($file = readdir($handle))) {
foreach($exts as $ext) { // for each extension check the extension
if (preg_match('/\.'.$ext.'$/i', $file, $test)) { // faster than ereg, case insensitive
$files[] = $file; // it's good
++$i;
}
}
}
closedir($handle); // We're not using it anymore
mt_srand((double)microtime()*1000000); // seed for PHP < 4.2
$rand = mt_rand(0, $i); // $i was incremented as we went along

header('Location: '.$folder.$files[$rand]); // Voila!
?>