DateInterval::$from_string undefined until a lookup

Description

The following code:

<?php
$dateInterval = new DateInterval('PT1S'); // or even DateInterval::createFromDateString('1 second')

var_dump(isset($dateInterval->from_string));

(array) $dateInterval; // or print_r() or var_dump()

var_dump(isset($dateInterval->from_string));

Resulted in this output:

bool(false)
bool(true)

But I expected this output instead:

bool(true)
bool(true)

According documentation property $from_string should be always defined (in PHP >= 8.2) but it isn't. Dump of the object initializes the property "ad hoc". var_dump() shouldn't have side effects IMHO.

PHP Version

PHP 8.2.20

Operating System

No response