title: Mark forum as read when user reads it, then mark as new when new reply is posted
body: <p>Ive got two tables, One for topics and one for replys.</p>
  
  <pre><code>+------------------+     +------------------+
  | forum_topics     |     | forum_posts      |
  +------------------+     +------------------+
  | topic_id         |     | post_id          |
  | topic_title      |     | post_content     |
  | topic_contents   |     | post_date        |
  | topic_date       |     | topic_id         |
  | topic_keywords   |     |                  |
  +------------------+     +------------------+
  </code></pre>
  
  <p>I want it so when a user views the page with the topic on and reads the topic it gets marked as read for that specific user. But if another user comes and replies to that thread, I want it to marked as new post since last visit or somthing similar.</p>
  
  <p>Any ideas?</p>
  
  <p>Thanks in advance.</p>