Generowanie linków do listy folderów

function foldery() {

    global $fa;
    $dir = dir("/usr/strony/$fa/");

    while (false !== ($folder = $dir->read())) {
            echo "<a href='index.php?action=lista&fa=$fa/$folder'>" . $folder."</a><br>";
    }
    $dir->close();
}
echo foldery();