League\Period\Period::getTimestampInterval PHP Method

    public function getTimestampInterval()
    {
        return $this->endDate->getTimestamp() - $this->startDate->getTimestamp();
    }

 /**
  * Returns the difference between two Period objects expressed in seconds
  *
  * @param Period $period
  *
  * @return float
  */
 public function timestampIntervalDiff(Period $period)
 {
     return $this->getTimestampInterval() - $period->getTimestampInterval();
 }