1--TEST-- 2Inherited DateTimeInterval serialisation with custom properties 3--FILE-- 4<?php 5date_default_timezone_set("Europe/London"); 6 7class MyDateInterval extends DateInterval 8{ 9 public function __construct( 10 string $duration, 11 public ?bool $myProperty = null, 12 ) { 13 parent::__construct($duration); 14 } 15} 16 17$d = new MyDateInterval("P1W2D", myProperty: true); 18$e = unserialize(serialize($d)); 19var_dump($e->myProperty); 20?> 21--EXPECTF-- 22bool(true) 23