title: Modify microseconds of a PHP DateTime object
body: <p>I have a PHP DateTime object with microseconds created as follows:</p>
  
  <pre><code>$time = microtime(true);
  $microseconds = sprintf('%06d', ($time - floor($time)) * 1000000);
  
  $dt = new DateTime(date('Y-m-d H:i:s.' . $microseconds, $time));
  </code></pre>
  
  <p>How can I modify the microseconds value of <code>$dt</code>, without creating a completely new DateTime instance?</p>