/**
** 截取中文字符串
**/
function msubstr($str, $start=0, $length, $charset="utf-8", $suffix=true){
 if(function_exists("mb_substr")){
 $slice= mb_substr($str, $start, $length, $charset);
 }elseif(function_exists('iconv_substr')) {
 $slice= iconv_substr($str,$start,$length,$charset);
 }else{
 $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));
 } 
 $fix='';
 if(strlen($slice) < strlen($str)){
  $fix='...';
 }
 return $suffix ? $slice.$fix : $slice;
}