/**
*生成随机数,可用户验证码
*@param
*/
function randStr($m = 5) {
$new_str = '';
$str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwsyz0123456789';
$max=strlen($str)-1;
for ($i = 1; $i <= $m; ++$i) {
$new_str .=$str[mt_rand(0, $max)];
}
return $new_str;
}