This tutorial describes a PHP-Nuke Function to restrict access by page as public or private. The function pageStatus(); is called on the top (or inside your root level header, not the themes header) of all pages. This will allow you to deifne in your admin panel specifc pages and urls that you want to have a particular viewing status. It explains a few ways to go about defining which pages to have the "public" or "private" status. Also the code for the function is available.
PHP pages have a reputation of being more difficult (or at least different) to SEO than static HTML pages. Here’s an overview of the major issues encountered when trying to make PHP scripts rank well. While this focuses on PHP much of it is still relevant to dynamic pages in general.
Metatags are a way for you to define your web page and web site to the outside world. You can declare the title, keywords and description, which help your placement in search engines. In addition, you can specify who owns the copyright, how often the page is to be visited by search engines and many other useful pieces of information.