Panda

<?php

$array = array(
"img/1.gif",
"img/2.png",
"img/3.jpg",
//"",
);
$file = $array[rand(0,2)];
if (file_exists($file)) {
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename='.basename($file));
    header('Expires: 0');
    header('Cache-Contrl: must-revalidate');
    header('Pragma: public');
    header('Content-Length: ' . filesize($file));
    ob_clean();
    flush();
    readfile($file);
    exit;
}

//echo $file;

?>