need multiple random images - every call to php from html begins the randomization again, causing duplicates

html calling for a random image:

<img src="/test/art/rotate.php?i=0">
<img src="/test/art/rotate.php?i=1">
<img src="/test/art/rotate.php?i=2">

php file i'm accessing:

<?php

// rotate images randomly but w/o dups on same page - format:

// <img src='rotate.php?i=0'> - rotate image #0 - use 'i=1'

// for second, etc

// (c) 2004 David Pankhurst - use freely, but please leave in my credit
$images = array_unique($images);
$images=array( // list of files to rotate - add as needed


  "img5.jpg",

  "img6.jpg",

  "img7.jpg",

  "img8.jpg",

  "img9.jpg",

  "img10.jpg",

  "img11.jpg",

  "img12.jpg",   

  "img13.jpg",

  "img14.jpg",

  "img15.jpg",  

  "img16.jpg",   );


$total=count($images);

$secondsFixed=3600; // seconds to keep list the same

$seedValue=(int)(time()/$secondsFixed);

srand($seedValue);

for ($i=0;$i<$total;++$i) // shuffle list 'randomly'

{

  $r=rand(0,$total-1);

  $temp =$images[$i];

  $images[$i]=$images[$r];

  $images[$r]=$temp;

}

$index=(int)($_GET['i']); // image index passed in

$i=$index%$total; // make sure index always in bounds

$file=$images[$i];

header("Location: $file"); // and pass file reference back

?>

I get images to display, but there are duplicates. I think this is because every call to the php file is a new call, the already loaded images aren't remembered as already loaded. How do I prevent showing duplicates?