Description:
------------
Upon calling var_dump() or array_key_exists() on a \DateTime object, it will receive new public properties not accessible before.

Test script:
---------------
$object = new DateTime();
array_key_exists("test",$object);
var_dump($object->date);



Expected result:
----------------
The result should be the same regardless of the arbitrary calls ( probably fields should not exist at all )

Actual result:
--------------
For the code using array_key_exists/var_dump, we receive a string from the public field.

Otherwise we receive a warning.