title: What are the possible results of PDO::getAttribute(PDO::ATTR_CONNECTION_STATUS)
body: <p>I have been looking in to this almost all day.. and can't seem to find the values returned anywhere. Can somebody tell me:</p>
  
  <ol>
  <li>What values do <code>PDO::getAttribute(PDO::ATTR_CONNECTION_STATUS);</code> return?</li>
  <li>Is it possible to rely on its result to determinate if the connection is still alive?(And eventually, what could I use to check if the connection is still alive?)</li>
  </ol>