title: PHP oldest path based on a dir name
body: <p>I have on my linux machine such folder tree structure:<br />
  <code>/dir/yyyy/mm/dd/HH</code><br />
  <br />
  e.g.:<br />
  <code>/dir/2014/03/01/08</code><br />
  <code>/dir/2014/03/20/09</code><br />
  <code>/dir/2014/03/01/10</code><br />
  <code>/dir/2014/08/01/10</code><br />
  <code>/dir/2014/12/15/10</code><br />
  <code>/dir/2015/01/01/14</code></p>
  
  <p>I'd like to get in php what path is the oldest, like this:<br />
  The oldest path is: <code>2014-03-01 08</code><br />
  The newest path is: <code>2015-01-01 14</code></p>
  
  <p>How it can be done?</p>