2
drop the include - that's for including the XoopsForm framework for easy form building.
Your code for a PHP block (do you mean a custom PHP block or one in a module?) should be this:
$member_handler =& xoops_gethandler('member');
$criteria = new Criteria('level', 0, '>');
$total = $member_handler->getUserCount($criteria);
$midnight = mktime(0, 0, 0, date('n', time()), date('j', time()), date('Y', time()));
$criteria = new CriteriaCompo($criteria);
$criteria->add(new Criteria('user_regdate', $midnight, ">"));
$newtoday = $member_handler->getUserCount($criteria);
Depending on whether you are using a custom PHP block or a block in a module, the way to display it will be a little different.