Randomize slideshow images - php

Question

I have this drupal slideshow which pulls images from a folder sequentially by image title (01_title.jpg, 02_title.jpg, etc..)
I was wondering if there is an easy way to randomize the images, so it starts with a different image every time you refresh the page?
you can view the slideshow here http://www.rubensteinpr.com/
Thanks!
<div id ="index">
<?php
// Note that !== did not exist until 4.0.0-RC2
$desired_extension = 'jpg'; //extension we're looking for
$banner_imgs_array = array(); // array of banner images
$banner_imgs = ''; // sting of banner images names comma dileneated
if ($handle = opendir(file_directory_path().'/banner_imgs')) {
/* This is the correct way to loop over the directory. */
while (false !== ($file = readdir($handle))) {
if(($file != ".") and ($file != "..")) {
$fileChunks = explode(".", $file);
if($fileChunks[1] == $desired_extension) //interested in second chunk only
{
$banner_imgs_array[] = $file;
}
}
}
closedir($handle);
$banner_imgs = implode(',', $banner_imgs_array);
}
?>
<div id="banner"><img src="<?php print file_directory_path(); ?>/temp_banner.jpg" width="702" height="310" border="0"></div>
<div id="bannerText">media relations • strategic planning • digital communications • crisis management</div>
<script type="text/javascript">
// <![CDATA[
var so = new SWFObject("<?php print file_directory_path(); ?>/banner.swf", "ban", "702", "310", "8", "#ffffff");
so.addParam('menu', 'false');
so.addParam("wmode", "transparent");
so.addParam("base", "<?php print file_directory_path(); ?>");
so.addVariable("banner_imgs", "<?php print $banner_imgs; ?>");
so.write("banner");
// ]]>
</script>
</div>

Answer 1

adding
shuffle($banner_imgs_array);
line just before
$banner_imgs = implode(',', $banner_imgs_array);
should do the trick.

Answer 2

array_rand will return one or more random array keys. If you want to shuffle the array itself, use shuffle.