DateInterval::$from_string undefined until a lookup

[esler]

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

[hormus]

Maybe missing read property date_interval_read_property "from_string".
Example patch for Old bug (DateInterval and isset) #1877
Alternative use foreach

<?php

/* from PHP 8.2 from_string boolean property
To use an ISO-8601 format string like P7D, 
you must use the constructor.*/
$dateInterval = new DateInterval('P2DT1S');
//dateInterval = DateInterval::createFromDateString('2 day 1 second');

$from_string = null;
foreach($dateInterval as $prop => $val) {
    if('from_string' == $prop) {
        $from_string = $val;
    }
}
$intervalday = $dateInterval->d;

var_dump($intervalday, $from_string);
?>

Expected result PHP 8.2:

int(2)
bool(false)

[kocsismate]

Yes, DateInterval unfortunately uses dynamic properties... I have a patch in review state which would declare the properties: #13050