1. /**
    2.  * utf8转gbk
    3.  * @param $utfstr
    4.  */
    5. function utf8_to_gbk($utfstr) {
    6.    global $UC2GBTABLE;
    7.    $okstr = '';
    8.    if(empty($UC2GBTABLE)) {
    9.       $filename = CODETABLEDIR.'gb-unicode.table';
    10.       $fp = fopen($filename, 'rb');
    11.       while($l = fgets($fp,15)) {        
    12.          $UC2GBTABLE[hexdec(substr($l, 7, 6))] = hexdec(substr($l, 0, 6));
    13.       }
    14.       fclose($fp);
    15.    }
    16.    $okstr = '';
    17.    $ulen = strlen($utfstr);
    18.    for($i=0; $i<$ulen; $i++) {
    19.       $c = $utfstr[$i];
    20.       $cb = decbin(ord($utfstr[$i]));
    21.       if(strlen($cb)==8) { 
    22.          $csize = strpos(decbin(ord($cb)),'0');
    23.          for($j = 0; $j < $csize; $j++) {
    24.             $i++; 
    25.             $c .= $utfstr[$i];
    26.          }
    27.          $c = utf8_to_unicode($c);
    28.          if(isset($UC2GBTABLE[$c])) {
    29.             $c = dechex($UC2GBTABLE[$c]+0x8080);
    30.             $okstr .= chr(hexdec($c[0].$c[1])).chr(hexdec($c[2].$c[3]));
    31.          } else {
    32.             $okstr .= '&#'.$c.';';
    33.          }
    34.       } else {
    35.          $okstr .= $c;
    36.       }
    37.    }
    38.    $okstr = trim($okstr);
    39.    return $okstr;
    40. }