title: Getting first and last week in an month
body: <p>I have been trying to find the first and last week in an month with strtotime</p>
  
  <pre><code>$year = 2013;
  $month = 12;
  
  $first_week = date("W", strtotime('first week '.$year.'-'.$month));
  $last_week = date("W", strtotime('last week '.$year.'-'.$month));
  </code></pre>
  
  <p>Result:</p>
  
  <pre><code>$first_week = 49
  $last_week = 47
  </code></pre>
  
  <p>Strange result, how to get the right results?</p>