Description:
------------
The DateInterval does not seem to expose its properties to var_dump().. 

Reproduce code:
---------------
bjori@lohan:~$ cat test.php 
<?php

$date = new DateTime("28-July-2008");
$other = new DateTime("31-July-2008");

$diff = date_diff($date, $other);

var_dump($diff);
echo $diff, "\n";

bjori@lohan:~$ ~/php/5.3/sapi/cli/php test.php 
object(DateInterval)#3 (0) {
}

Catchable fatal error: Object of class DateInterval could not be converted to string in /crypto/bjori/test.php on line 9


Expected result:
----------------
The properties to retrieve the actual difference.