DateTimeImmutable::add()

(PHP 5 >= 5.5.0, PHP 7)

Adds an amount of days, months, years, hours, minutes and seconds

说明

publicDateTimeImmutable::add(DateInterval$interval): DateTimeImmutable

LikeDateTime::add()but works withDateTimeImmutable.

Please note, add() works a litte different than for DateTime-Objects.
Since DateTimeImmutable is in fact immutable. A line like this will not work:
  $di = new DateTimeImmutable("2018-12-12T10:00:00");
  $di->add(new DateInterval('PT45M')); // $di unchanged !!!
compared to
  $dt = new DateTime("2018-12-12T10:00:00");
  $dt->add(new DateInterval('PT45M')); // added 45 minutes
so you need to write
  $di = new DateTimeImmutable("2018-12-12T10:00:00");
  $di = $di->add(new DateInterval('PT45M')); // $di now changed