Description:
------------
The DatePeriod instance does not expose its internal properties, thus makes impossible to extend the class.

The properties are not visible in the reflection as well. Also, when I cast the instance to array (which usually exposes all properties), no props are shown.

The draft of the test follows.

Test script:
---------------
$dp = new DatePeriod(new DateTime('2010-01-01'), new DateInterval('P1D'), 2);
$r = new ReflectionObject($dp);
$arr = (array)$dp; // cast to array to see the values of propeties

echo "Properties:\r\n";
foreach($r->getProperties() as $v) {
	echo $v->getName()."\r\n";
}
echo "\r\n";

echo "Methods:\r\n";
foreach($r->getMethods() as $v) {
	echo $v->getName()."\r\n";
}
echo "\r\n";

echo "Array cast:\r\n";
echo strtr(print_r($arr, true), "\0", '_');

Expected result:
----------------
Properties:
any_valid_properties...
...listed_here_after_implementing

Array cast:
Array
(
   any_valid_properties...
   ...listed_here_after_implementing
)


Actual result:
--------------
Properties:

Array cast:
Array
(
)