<?php
/*
  *   Author:   http://www.yox.net.ru
*/

$url = "./images"; //注意:图片文件夹路径，不可含有'/'；
$files = array();
if(false !== ($handle = @opendir($url)))
{
  while($file = readdir($handle))
{
if(($file !== ".")&&($file !== ".."))
{
  if((substr($file,-3) == "gif") || (substr($file,-3) == "jpg") || (substr($file,-3) == "png"))
   $files[count($files)] = $file;
}
}

closedir($handle);
$random = rand(0,(count($files)-1)); //设定随机数的范围;

//根据文件类型,设置输出的文件类型;
if(substr($files[$random],-3) == "gif")
    header("Content-type:image/gif");

elseif(substr($files[$random],-3) == "jpg")
   header("Content-type:image/jpeg");

elseif(substr($files[$random],-3) == "png")
   header("Content-type:image/png");
   readfile("$url/$files[$random]"); //读文件,显示图片;
}else
  echo "<b>图片目录<font color=red>$url</font>不存在!请重新设置!</b>";
?>

<?readfile(rand(1,15).".gif");?>