<?php
/*
How to use:
1. Place suitable images in the same folder as the script resides.
The images should have a .jpg, .gif or a .png ending.

2. Copy the source of this script in a textfile, rename it avatar.php
(or any other name, as you please) and save it in the same directory as the images.

3. Call the script by appending a random name with the filetype ending.
Example:
http://www.fungifun.org/rotate/avatar.php/example.jpg

avatar.php is the name of the script

example.jpg is a random name, you could also use asasd.jpg or qwfpoa.jpg, the name doesn't matter,
what is important is the ending. The ending determines which files from the folder are used.
So, if you use example.gif, then the gif files in this folder will be used.
*/

$filetype = end(explode(".",$_SERVER['REQUEST_URI']));
if($filetype != "jpg" && $filetype != "gif" && $filetype != "png") exit;
if ($handle = opendir('.')) {
   while (false !== ($file = readdir($handle))) {
       if ($file != "." && $file != ".." && stristr($file, ".".$filetype)) $files[]=$file;
   }
   closedir($handle);
}
if ($files) {
    $imagenr = rand(0, sizeof($files)-1);
    if($filetype == "jpg") $filetype = "jpeg";
    $fp = fopen($files[$imagenr], 'rb');
    header("Content-Type: image/$filetype");
    header("Content-Length: " . filesize($files[$imagenr]));
    fpassthru($fp);
    exit;
}
?> 

header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); 
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache");
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Content-Type: image");