ciao, prova così:
codice:
if ($handle = opendir('news')) {
	while (false !== ($file = readdir($handle)))
	if (preg_match ("/^news./", $file)) {
		$expl=explode("-",$file);
		$time= mktime (0,0,0,$expl[2],$expl[1],$expl[3]);
		$prova[$file]=$time;
	}
}
asort($prova);
reset($prova);
foreach(array_slice($prova,-3) as $chiave=>$valore)
	echo "$chiave = $valore\n
";
closedir($handle);