PHP中指定GB2312编码文字转换成UTF-8编码的类方法

  /**
   * gb2utf8 指定的文字转换为UTF-8格式，包括中英文混合
   * $gb 传过来的GB字符，下面的方法类似
   */
  function gb2utf8($gb) {
    if(!trim($gb))
    return $gb;
    $filename="./gb2312.txt";
    $tmp=file($filename);
    $codetable=array();
    while(list($key,$value)=each($tmp))
      $codetable[hexdec(substr($value,0,6))]=substr($value,7,6);
      $utf8="";
    while($gb) {
      if (ord(substr($gb,0,1))>127) {
        $tthis=substr($gb,0,2);
        $gb=substr($gb,2,strlen($gb)-2);
        $utf8.=$this->u2utf8(hexdec($codetable[hexdec(bin2hex($tthis))-0x8080]));
      }  else {
        $tthis=substr($gb,0,1);
        $gb=substr($gb,1,strlen($gb)-1);
        $utf8.=$this->u2utf8($tthis);
      }
    }
  
    return $utf8;
  }

  function u2utf8($c) {
    $str="";
    if ($c < 0x80) {
      $str.=$c;
    } else if ($c < 0x800) {
      $str.=chr(0xC0 | $c>>6);
      $str.=chr(0x80 | $c & 0x3F);
    } else if ($c < 0x10000) {
      $str.=chr(0xE0 | $c>>12);
      $str.=chr(0x80 | $c>>6 & 0x3F);
      $str.=chr(0x80 | $c & 0x3F);
    }
    else if ($c < 0x200000) {
      $str.=chr(0xF0|$c>>18);
      $str.=chr(0x80|$c>>12&0x3F);
      $str.=chr(0x80|$c>>6&0x3F);
      $str.=chr(0x80|$c&0x3F);
    }
    return$str;
  }