PHP function to list all subdirectories in a directory

The following function lists all subdirectories in a directory:

function listdir($dir){
 if ($handle = opendir($dir)){
 $output = array() ;
 while (false !== ($item = readdir($handle))){
 if (is_dir($dir.'/'.$item) and $item != "." and $item != ". ."){
 $output[] = $dir.'/'.$item;
 $output = array_merge($output, ListDescendantDirectories($dir.'/'.$item));
 }
 }
 closedir( $handle);
 return $output;
 }else{
 return false;
 }
}

$dirs = listdir('myDirectory');
foreach($dirs as $dir){
 echo $dir.'< ;br>';
}
?>

Directory, PHP