Can I Randomize Images From Database?

I found this javascript to randomize an image on a page...

Code:

<script language="JavaScript" type="text/javascript">
<!--
function random_img(){
var ranimage = new Array();
ranimage[1] = "photo1.jpg";
ranimage[2] = "photo2.jpg";
ranimage[3] = "photo3.jpg";

var ry = Math.floor(Math.random()*ranimage.length)
if (ry==0)
ry=1
document.write('<img src="'+ranimage[ry]+'" border=1>');
}
random_img();
// -->
</script>

I have some images that are dynamically generated and i want these images to randomize every few seconds (at the moment the images change when the user goes to a different page on the site)...can anyone give me any ideas as to whether this is possible??

The PHP code i'm using is below...

<?php

// read image dir
$dir="../../admin/uploads/";
// Open directory, and proceed to read its contents
if (is_dir($dir)) {
if ($dh = opendir($dir)) {
while (($file = readdir($dh)) !== false) {
if (filetype($dir . $file)== "file"){

$counter++;

$selectSQL = "SELECT id, url, imagefile from images";
$result=mysql_query($selectSQL);
#print $result . " - " . mysql_error();

$nameStack=array();
$urlStack=array();

while ($row = mysql_fetch_assoc($result)){
$thisurl= $row['url'];
$thisid= $row['id'];

array_push($nameStack, $row['imagefile']);
array_push($urlStack, $row['url']);

}


}
}
closedir($dh);
}
}


// load each image into array echo rand(5, 15);
// get count of total no. of images
$lastNo=sizeof($urlStack)-1;
$imageToUse=rand(0,$lastNo);
#print "using image $imageToUse of $lastNo";
$imageName=$nameStack[$imageToUse];
$imageUrl=$urlStack[$imageToUse];

#print "got $imageUrl and $imageName
";

//

?>

<a href="<?php echo $imageUrl; ?>"><img src="http://mywebsite.com/admin/uploads/<?php echo $imageName; ?>" alt="click here for our special offers" border=0 /></a>