<?php

$date = (new ReflectionClass(DateTime::class))->newInstanceWithoutConstructor();
new DatePeriod($date, new DateInterval('P1D'), 2);

<?php

$date = (new ReflectionClass(DateTime::class))->newInstanceWithoutConstructor();
$dateperiod = (new ReflectionClass(DatePeriod::class))->newInstanceWithoutConstructor();
$dateperiod->__unserialize(['start' => $date]); // __wakeup is also affected