验证码：

$mid = (isset($mid) && is_numeric($mid)) ? $mid : 0;

$validate = empty($validate) ? '' : strtolower(trim($validate));
$svali = strtolower(GetCkVdValue());
if($validate=='' || $validate != $svali)
{
	ResetVdValue();
	ShowMsg('验证码不正确!',$_SERVER["HTTP_REFERER"],1000);
	exit();
}