/******************************
//utf-8 轉gb編碼
*******************************/
function utf82gb($utfstr)
{
 global $uc2gbtable;
 $okstr = "";
 if(trim($utfstr)=="") return $utfstr;
 if(empty($uc2gbtable)){
  $filename = dirname(__file__)."/data/gb2312-utf8.table";
  $fp = fopen($filename,"r");
  while($l = fgets($fp,15))
  { $uc2gbtable[hexdec(substr($l, 7, 6))] = hexdec(substr($l, 0, 6));}
  fclose($fp);
 }
 $okstr = "";
 $ulen = strlen($utfstr);
 for($i=0;$i<$ulen;$i++)
 {
  $c = $utfstr[$i];
  $cb = decbin(ord($utfstr[$i]));
  if(strlen($cb)==8){
   $csize = strpos(decbin(ord($cb)),"0");
   for($j=0;$j < $csize;$j++){
    $i++; $c .= $utfstr[$i];
   }
   $c = utf82u($c);
   if(isset($uc2gbtable[$c])){
    $c = dechex($uc2gbtable[$c]+0x8080);
    $okstr .= chr(hexdec($c[0].$c[1])).chr(hexdec($c[2].$c[3]));
   }
   else
   { $okstr .= "&#".$c.";";}
  }
  else $okstr .= $c;
 }
 $okstr = trim($okstr);
 return $okstr;
}