randimage.

<?
/*
+---------------------------------------------------------+
| By Bleakwind http://www.weaverdream.com
+---------------------------------------------------------+
*/
$dir = "images/";//图片目录,注意是按照名字排序显示的...
$imgwidth = 0;//图片宽度,为0则为原始大小
$iforder = 1;//顺序显示还是随机显示,1为顺序显示,0为随机显示
$ifcircle = 0;//顺序显示的时候是否循环播放,1为循环播放,0为不循环

_start();
if($imgwidth==0){$imgwidth=="";}else{$imgwidth=="width='".$imgwidth."'";}
$handle=opendir($dir);
while ($file_name=readdir($handle)){
if(($file_name!==".")&&($file_name!=="..")){$file_list[]=$file_name; }
}
closedir($handle);

if($iforder==1){
if(isset($_['sess_order'])){
if($_['sess_order']<count($file_list)-1){
$_['sess_order']++;
}else{
if($ifcircle == 1){
$_['sess_order']=0;
}
}
}else{
$_['sess_order']=0;
}
$i=$_['sess_order'];
}else{
$num=count($file_list)-1;
$i=rand(0,$num);
}

readfile($dir.$file_list[$i]);
?>

调用
<img src="randimage." border="0">