PHP에서 두 개의 날짜 간격을 추가하는 방법은 무엇입니까?

<code class="php">interval 1: 03:05
interval 2: 05:00
Total interval : 08:05</code>

<code class="php">$e = new DateTime('00:00');
$f = clone $e;
$e->add($interval1);
$e->add($interval2);
echo "Total interval : " . $f->diff($e)->format("%H:%I") . "\n";</code>

<code class="php">class MyDateInterval extends DateInterval
{
    public static function fromDateInterval(DateInterval $from)
    {
        return new MyDateInterval($from->format('P%yY%dDT%hH%iM%sS'));
    }
                                  
    public function add(DateInterval $interval)
    {
        foreach (str_split('ymdhis') as $prop)
        {
            $this->$prop += $interval->$prop;
        }
    }
}

$a = new DateTime('14:25');
$b = new DateTime('17:30');
$interval1 = $a->diff($b);
echo "interval 1: " . $interval1->format("%H:%I") . "\n";

$c = new DateTime('08:00');
$d = new DateTime('13:00');
$interval2 = $c->diff($d);
echo "interval 2: " . $interval2->format("%H:%I") . "\n";
                                  
$e = MyDateInterval::fromDateInterval($interval1);
$e->add($interval2);
echo "Total interval: " . $e->format("%H:%I") . "\n";</code>