title: How create "All edits are tracked"
body: <p>I'm using PHP (Yii-framework) and MySQL database on my site.</p>
  
  <p>Users can post and edit some articles.
  How can I store every edit version like here in SO?
  (Like Wikipedia, this site is collaboratively edited, and <strong>all edits are tracked</strong>)</p>
  
  <p>What sould I use and how? Database structure? Some libraries?
  What keywords should I use to google? :)</p>
  
  <p><strong>UPD</strong>. And how to display changes between revisions, like here in SO?</p>
  
  <p>Thanks</p>