Thumbnail casuali in PHP

Salve, ho scovato questo script su internet per prelevare un'immagine a caso da una cartella (in questo caso /images/)

<?php
/*******************************************************************************
*  Title: Random image script (RandIm)
*  Version: 1.0 @ January 3, 2009
*  Author: Klemen Stirn
*  Website: http://www.phpjunkyard.com
********************************************************************************
*  COPYRIGHT NOTICE
*  Copyright 2009 Klemen Stirn. All Rights Reserved.
*
*  This script may be used and modified free of charge by anyone
*  AS LONG AS COPYRIGHT NOTICES AND ALL THE COMMENTS REMAIN INTACT.
*  By using this code you agree to indemnify Klemen Stirn from any
*  liability that might arise from it's use.
*
*  If you are using this script you are required to place a link
*  to PHPJunkyard on your website. You will find some link suggestions here:
*  http://www.phpjunkyard.com/link2us.php
*
*  Selling the code for this program, in part or full, without prior
*  written consent is expressly forbidden.
*
*  Obtain permission before redistributing this software over the Internet
*  or in any other medium. In all cases copyright and header must remain
*  intact. This Copyright is in full effect in any country that has
*  International Trade Agreements with the United States of America or
*  with the European Union.
*******************************************************************************/

/*******************************************************************************
*  SETTINGS
*
*  See readme.htm file for further instructions!
*******************************************************************************/

/* The default folder with images */
$settings['img_folder'] = 'images/';

/* File types (extensions) to display */
$settings['img_ext'] = array('.jpg','.gif','.png');

/*
   How to display the images?
   0 = print just the image path (for includes), like: images/test.jpg
   1 = redirect to the image, when using: <img src="randim.php" />
*/
$settings['display_type'] = 1;

/* Allow on-the-fly settings override? 0 = NO, 1 = YES */
$settings['allow_otf'] = 1;


/*******************************************************************************
*  DO NOT EDIT BELOW...
*
*  ...or at least make a backup before you do!
*******************************************************************************/

/* Override type? */
if ($settings['allow_otf'] && isset($_GET['type']))
{
    $type = intval($_GET['type']);
}
else
{
    $type = $settings['display_type'];
}

/* Override images folder? */
if ($settings['allow_otf'] && isset($_GET['folder']))
{
    $folder = htmlspecialchars(trim($_GET['folder']));
    if (!is_dir($folder))
    {
        $folder = $settings['img_folder'];
    }
}
else
{
    $folder = $settings['img_folder'];
}

/* Make sure images fodler ends with an '/' */
if (substr($folder,-1) != '/')
{
    $folder.='/';
}

/* Get a list of all the image files */
$flist = array();
foreach($settings['img_ext'] as $ext)
{
    $tmp = glob($folder.'*'.$ext);
    if (is_array($tmp))
    {
        $flist = array_merge($flist,$tmp);
    }
}

/* If we have any images choose a random one, otherwise select the "noimg.gif" image */
if (count($flist))
{
    $src = $flist[array_rand($flist)];
}
else
{
    $src = 'noimg.gif';
}

/* Output the image according to the selected type */
if ($type)
{
    header('Location:'.$src);
    exit();
}
else
{
    echo $src;
}
?>

Fin qui niente di errato... Il problema è che come output, quando vado a fare il thumbnail io uso questo:

<a href="randim.php"><img src="randim.php" width="200" height="150"></a>

E quindi, anche se genera il thumbnail, quando clicco sull'immagine viene prelevata un'altra immagine a caso, diversa da quella mostrata in miniatura! Come rimedio?

Purtroppo così facendo stampa proprio testualmente il percorso dell'immagine, tipo /images/img1.jpg...... Anche sapendo questo, non c'è modo di usarlo come dicevo io?

[javascripter]

Modifica lo script così:

<?php
session_start();

function filter($v) {
    global $ext;
    $e = end(explode('.', $v));

    if(in_array($e, $ext))
        return true;
    return false;
}

/* configurazioni */
$path = 'cartella/'; // con lo slash finale.
$ext = array('jpg', 'gif', 'png');
/* fine configurazioni */

$files = array_filter(glob($path . '*.*'), 'filter');

if(isset($_GET['c'], $_SESSION['img']))
    $img = $_SESSION['img'];
else
    $img = $files[rand(0, count($files) - 1)];

$_SESSION['img'] = $img;

header('Location: ' . $img);
?>

E per fare il link usi:

<a href="randim.php?c"><img src="randim.php" width="200" height="150" alt="casuale"></a>

E' semplicemente perfetto! Grazie mille!