Someone

<?
  echo "<html><head><link rel='stylesheet' type='text/css' href='pictures.css' /></head><body>";

function scandir_recursive($path)
{
if (!is_dir($path)) return 0;
$list=array();
$directory = opendir("$path");
while ($file= readdir($directory)) 
  {
       if (($file<>".")&&($file<>"..")) 
        {  
           $f=$path."/".$file;
$f=preg_replace('/(\/){2,}/','/',$f);
if(is_file($f)) $list[]=$f;             
if(is_dir($f))
$list = array_merge($list ,scandir_recursive($f));                             
        }    
   }
closedir($directory);
return $list ;
}

$rootdirlist=array();
$list=scandir_recursive("pictures");
foreach($list as $l){
  $dirxplode=explode('/',$l,-1);
  $rootdir=$dirxplode[1];
  $addnewroot=array($rootdir);
    if (array_search($rootdir,$rootdirlist)==FALSE){
    $rootdirlist=array_merge($rootdirlist,$addnewroot);
    }
  }
  
  print_r($rootdirlist);
  
  echo "</body></html>";
?>