How should I start with OAuth server at PHP

Question

Have found the following example of OAuth server http://oauth.googlecode.com/svn/code/php/OAuth_TestServer.php

But it is unclear for me 1. How I should generate certificates

1. How I should specify access token/access token secret/request token/request token secret, should they stored in database? Should it regenerated for each request? What else I should store in database?

2. Where should I implement the verification of Access token?

Please advice