/**
* Add a duration to this one.
*
* For instance, PT1S + PT1S = PT2S.
*
* @param Duration|DateInterval $duration A Duration or DateInterval object.
*/
public function add($duration)
{
$d1 = $this->refDate;
$d2 = clone $d1;
if ($duration instanceof Duration) {
$toAdd = $duration;
} else {
$toAdd = new Duration('PT0S');
$toAdd->setInterval($duration);
}
$d2->add(new DateInterval($this->__toString()));
$d2->add(new DateInterval($toAdd->__toString()));
$interval = $d2->diff($d1);
$this->interval = $interval;
}
/**
* Create a Duration object from a DateInterval object.
*
* @param \DateInterval $interval
* @return \qtism\common\datatypes\Duration
*/
public static function createFromDateInterval(DateInterval $interval)
{
$duration = new Duration('PT0S');
$duration->setInterval($interval);
return $duration;
}
