$tree = new data_tree;

function list_files($directory, $subid)
{
	static $id_counts = 1;
	foreach(glob($directory) as $filename)
	{
		$tree->add($id_counts, $subid, $filename); // <<-- this line
		echo $filename . "<br>";
		if(is_dir($filename)) list_files($filename . "/*", $subid);
	}
}

list_files("*", 0);