Description:
------------
Always getting exception when creating ReflectionProperty object on dynamicly created property.
Discovered when I tried to use ReflectionProperty::isDefault().
I presume it returns true when property is created on compile-time and false when dynamicly created on run-time?

Reproduce code:
---------------
class x {
 public $x = 1;
 public $y = 1;
}

$o = new x;
$o->z = 1;

$reflector = new ReflectionProperty($o, 'z');

$d = $reflector->isDefault();

Expected result:
----------------
$d == false

Actual result:
--------------
Fatal error: Uncaught exception 'ReflectionException' with message 'Property x::$z does not exist' on line: $reflector = new ReflectionProperty($o, 'z');