Description:
------------
In PHP 7.4 behavior of `foreach (new DateTime() as $property => $value)` has changed. Prior to 7.4 foreach iterates through virtual properties of DateTime object. Since 7.4 it is treated as empty array, which makes it incosistent with `json_encode()` and `(array)` cast. Cast to array was already fixed in https://bugs.php.net/bug.php?id=78383

https://3v4l.org/h99LLn

Context - foreach approach is used in Json helper in Yii 2:
https://github.com/yiisoft/yii2/issues/17760
https://github.com/yiisoft/yii2/blob/a636ff916ac3a06756f37c0dbfb55994394a6a55/framework/helpers/BaseJson.php#L160-L166

Test script:
---------------
$date = new DateTime('2019-12-24');
$properties = [];
foreach ($date as $k => $v) {
    $properties[$k] = $v;
}
var_dump($date);
var_dump((array) $date);
var_dump($properties);
echo json_encode($date), "\n";
echo json_encode((array) $date), "\n";
echo json_encode($properties), "\n";

Expected result:
----------------
object(DateTime)#1 (3) {
  ["date"]=>
  string(26) "2019-12-24 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(16) "Europe/Amsterdam"
}
array(3) {
  ["date"]=>
  string(26) "2019-12-24 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(16) "Europe/Amsterdam"
}
array(3) {
  ["date"]=>
  string(26) "2019-12-24 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(16) "Europe/Amsterdam"
}
{"date":"2019-12-24 00:00:00.000000","timezone_type":3,"timezone":"Europe\/Amsterdam"}
{"date":"2019-12-24 00:00:00.000000","timezone_type":3,"timezone":"Europe\/Amsterdam"}
{"date":"2019-12-24 00:00:00.000000","timezone_type":3,"timezone":"Europe\/Amsterdam"}


Actual result:
--------------
object(DateTime)#1 (3) {
  ["date"]=>
  string(26) "2019-12-24 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(16) "Europe/Amsterdam"
}
array(3) {
  ["date"]=>
  string(26) "2019-12-24 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(16) "Europe/Amsterdam"
}
array(0) {
}
{"date":"2019-12-24 00:00:00.000000","timezone_type":3,"timezone":"Europe\/Amsterdam"}
{"date":"2019-12-24 00:00:00.000000","timezone_type":3,"timezone":"Europe\/Amsterdam"}
[]