Yes it is always better to see some of the existing open source php shopping cart scripts like for e.g opencart etc and learn from them.

'DATABASE_SERVER' => 'db.aa.0000000.hostedresource.com',

are you sure you need to specify the full host name while connecting ? Have you checked with your webhost ?

This article should help

Storing hierarchical data in database (http://www.sitepoint.com/article/hierarchical-data-database/)

Why don't you generate some MD5 hash for random numbers yourself ?

Would the first site's database get updated frequently.
If not you can achieve good performance if you run a cron script to transfer content from the first site's database to your other server...

You can run PHP via command line or via your web browser.

What happens if you type http://localhost/ in your browser ?

http://www.php.net/date should be of some help especially

I'm note sure , Do you want to include those files based on the query string ?

Yes I'm with sarah too. Once people see your knowledge, then projects will automatically flow.

Also phpbb has quite a number of mods

http://www.phpbb.com/mods/

which you can try out.

This

http://en.wikibooks.org/wiki/Wiki_Science:How_to_start_a_Wiki

should give you more information on hosting wiki