thinkphp 字符截取函数msubstr()

function msubstr($str, $start=0, $length, $charset="utf-8", $suffix=false){
 
 if(function_exists("mb_substr")){
 
  if($suffix)
 
   return mb_substr($str, $start, $length, $charset)."...";
 
  else
 
   return mb_substr($str, $start, $length, $charset);
 
 }elseif(function_exists('iconv_substr')) {
 
  if($suffix)
 
   return iconv_substr($str,$start,$length,$charset)."...";
 
  else
 
   return iconv_substr($str,$start,$length,$charset);
 
 }
 
 $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));
 
 if($suffix) return $slice."…";
 
 return $slice;
 
}