Hide custom page from guests?

[eNforce]

How can I hide one of my custom pages from guests and make the page prompt them to login/register? Basically what vBulletin already does, but for custom code.

Also, how can I require a member to have X amount of posts before he/she can access the custom page?

[Dismounted]

I'm assuming you have global.php included.
if (is_member_of($vbulletin->userinfo, 1))
{
print_no_permission();
}
if ($vbulletin->userinfo['posts'] >= 50)
{
eval(standard_error(fetch_error('ERROR_PHRASE')));
}