function is_valid_filename($name) 
{
  $parts = preg_split("/(\/|".preg_quote("\\").")/", $name);
  if (preg_match("/[a-z]:/i", $parts[0])) {
    unset($parts[0]);
  }
  foreach ($parts as $part) 
  {
    print "part = '$part'<br>";
    if (preg_match("/[".preg_quote("^|?*<\":>", "/")."\a\b\c\e\x\v\s]/", $part) || preg_match("/^(PRN|CON|AUX|CLOCK$|NUL|COMd|LPTd)$/im", 
    str_replace(".", "\n", $part))) {
      return false;
    }
  }
  return true;
}
$bad = array_merge(array_map('chr', range(0, 31)), array("<", ">", ":", '"', "/", "\\", "|", "?", "*"));
$result = str_replace($bad, "", $filename);