/**

  * 字符串截取，支持中文和其他编码

  * @param  [string]  $str     [字符串]

  * @param  integer $start   [起始位置]

  * @param  integer $length  [截取长度]

  * @param  string  $charset [字符串编码]

  * @param  boolean $suffix  [是否有省略号]

  * @return [type]           [description]

  */

 function msubstr($str, $start=0, $length=15, $charset="utf-8", $suffix=true) {

     if(function_exists("mb_substr")) {

         return mb_substr($str, $start, $length, $charset);

     } elseif(function_exists('iconv_substr')) {

         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;

 }

 /**

  * @计算中文字符串长度，只支持UTF8编码

  */

 function utf8_strlen($string = null) {

        preg_match_all(“/./us”, $string, $match);

        return count($match[0]);

 }