php在linux上遍历文件目录乱序问题

$dh = opendir($dir);
if ($dh) {
	while (false !== ($file = readdir($dh))) {
    if ($file != '.' && $file != '..' && strpos($file, "execute_dump") !== false) {
      $filename = $dir . $file;
      $file_time = filemtime($filename);
      if (time() - $file_time < 60) {
        continue;
      }
      $filelist[$file_time] = $file . "rn";
		}
	}
	closedir($dh);
}
ksort($filelist);