msubstr截取中文 stristr() 函数查找字符串在另一个字符串中第一次出现的位置

{$vons.title|msubstr=0,26} 像这样，总是显示错误，说msubstr函数未定义，
在使用这个函数之前是否需要引入什么文件？
Common/common.php中定义函数：

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

就是这么简单

  echop  sub_str

foreach($hot_goods_list AS $idx => $row){
  $hot_goods_list[$idx]['goods_name'] = $GLOBALS['_CFG']['goods_name_length'] > 0 ?
        sub_str($row['goods_name'], $GLOBALS['_CFG']['goods_name_length']) : $row['goods_name'];

}