php实现编码的转换,这里会把gb2312转换成utf-8

function gb2utf8($gb) {
 if( !trim($gb) ) return $gb;
 $utf8='';
 while($gb) {
     if( ord(substr($gb,0,1)) > 127 ) {
  $t=substr($gb,0,2);
  $gb=substr($gb,2);
  $utf8 .= $this->u2utf8($this->codetable[hexdec(bin2hex($t))-0x8080]);
     }
     else {
  $t=substr($gb,0,1);
  $gb=substr($gb,1);
  $utf8 .= $this->u2utf8($t);
     }
 }
 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;
    }

} 说一点,编码集我就不写出来了,用for一下就知道了.