//随机产生$num位字符串    function mkrandomstr($num=6){        $str="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";        $str=str_shuffle($str);        return substr($str, 0,$num);    }

//随机产生$num位字符串    function mkrandomstr($num=6)    {        $str="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";    $randStr = "";    for($i=0;$i<$num; $i++)    {        $rand = rand(0,62);        $randStr .= $str[$rand];    }    return $randStr;    }