title: how to convert minutes into microtime
body: <p>I have a session which contains <code>microtime(true)</code> value. like below:</p>
  
  <pre><code>Yii::app()-&gt;user-&gt;setState('portal_logged_time', microtime(true));
  </code></pre>
  
  <p>Now i want to add 15 minutes in above session, but it should remain in microtime.</p>
  
  <pre><code>$starttime = Yii::app()-&gt;user-&gt;getState('portal_logged_time');
  // Now i want to add microtime of 15 minutes into $starttime
  $endtime = // i want to do something like this ($starttime*15*60); 
  </code></pre>
  
  <p>I have tried this but it is not working <code>$starttime*15*60</code>.  </p>
  
  <p>So how to achieve that? </p>
  
  <p>After that i am trying to fetch remaining minutes and seconds:</p>
  
  <pre><code>$duration = $endtime-$starttime;
  
  $hours = (int)($duration/60/60);
  $minutes = (int)($duration/60)-$hours*60;
  $seconds = (int)$duration-$hours*60*60-$minutes*60;
  </code></pre>