3.2、gbk转utf8

/**
 * gbk转utf8
 * @param $gbstr
 */
function gbk_to_utf8($gbstr) {
   global $CODETABLE;
   if(empty($CODETABLE)) {
      $filename = CODETABLEDIR.'gb-unicode.table';
      $fp = fopen($filename, 'rb');
      while($l = fgets($fp,15)) { 
         $CODETABLE[hexdec(substr($l, 0, 6))] = substr($l, 7, 6); 
      }
      fclose($fp);
   }
   $ret = '';
   $utf8 = '';
   while($gbstr) {
      if(ord(substr($gbstr, 0, 1)) > 0x80) {
         $thisW = substr($gbstr, 0, 2);
         $gbstr = substr($gbstr, 2, strlen($gbstr));
         $utf8 = '';
         @$utf8 = unicode_to_utf8(hexdec($CODETABLE[hexdec(bin2hex($thisW)) - 0x8080]));
         if($utf8 != '') {
            for($i = 0; $i < strlen($utf8); $i += 3) $ret .= chr(substr($utf8, $i, 3));
         }
      } else {
         $ret .= substr($gbstr, 0, 1);
         $gbstr = substr($gbstr, 1, strlen($gbstr));
      }
   }
   return $ret;
}