file to utf8

function readfile2utf8($filename) {
  $content = file_get_contents($filename);
  // return mb_convert_encoding($content, 'UTF-8',
  //     mb_detect_encoding($content, 'UTF-8, ISO-8859-1', true));
  return iconv(mb_detect_encoding($content, mb_detect_order(), true), "UTF-8", $content);
}