PHP实现中文字串截取无乱码的方法

function GBsubstr($string, $start, $length) {
if(strlen($string)>$length){
   $str=null;
   $len=$start+$length;
   for($i=$start;$i<$len;$i++){
    if(ord(substr($string,$i,1))>0xa0){
     $str.=substr($string,$i,2);
     $i++;
    }else{
     $str.=substr($string,$i,1);
    }
   }
   return $str.'...';
}else{
   return $string;
}
}

【实现中文字串截取无乱码的方法--适用于utf-8】

function substr_text($str, $start=0, $length, $charset="utf-8", $suffix="")
{
if(function_exists("mb_substr")){
return mb_substr($str, $start, $length, $charset).$suffix;
}
elseif(function_exists('iconv_substr')){
return iconv_substr($str,$start,$length,$charset).$suffix;
}
$re['utf-8']  = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|[\xe0-\xef][\x80-\xbf]{2}|[\xf0-\xff][\x80-\xbf]{3}/";
$re['gb2312'] = "/[\x01-\x7f]|[\xb0-\xf7][\xa0-\xfe]/";
$re['gbk']    = "/[\x01-\x7f]|[\x81-\xfe][\x40-\xfe]/";
$re['big5']   = "/[\x01-\x7f]|[\x81-\xfe]([\x40-\x7e]|\xa1-\xfe])/";
preg_match_all($re[$charset], $str, $match);
$slice = join("",array_slice($match[0], $start, $length));
return $slice.$suffix;
}