Description:
------------
When serializing an object with a __sleep method defined, the original object may be modified by __sleep.  I'd like to see the __sleep method always being called on a copy of the object being serialized and not on the actual object.  In PHP4, this is _mostly_ the case as long as you're not working with references, but in PHP5, the original object is always modified directly.

The example below is a little contrived, but does demonstrate the idea.  Under PHP4, the result is _almost_ as expected, except that the instance of B referenced by $a->b is modified.  If the reference is changed to a plain copy (change the line reading "$a->b = &$b;" to "$a->b = $b;"), then the instance is not modified.

PHP5 gives the output given under actual result, which is probably wrong in either case.

Reproduce code:
---------------
<?php
class B {
  var $b = 'default';
  function __sleep() {
    $this->b = 'serialized';
    return Array('b');
  }
}

class A {
  var $a = "default";
  var $b = null;

  function __sleep() {
    $this->a = "serialized";
    return array_keys(get_object_vars($this));
  }
}


$a = new A();
$b = new B();
$a->b = &$b;
print_r($a);

$s = serialize($a);
print_r($s);
print_r($a);

$na = unserialize($s);
print_r($na);
?>

Expected result:
----------------
a Object
(
    [a] => default
    [b] => b Object
        (
            [b] => default
        )

)
O:1:"a":2:{s:1:"a";s:10:"serialized";s:1:"b";O:1:"b":1:{s:1:"b";s:10:"serialized";}}a Object
(
    [a] => default
    [b] => b Object
        (
            [b] => default
        )

)
a Object
(
    [a] => serialized
    [b] => b Object
        (
            [b] => serialized
        )

)

Actual result:
--------------
A Object
(
    [a] => default
    [b] => B Object
        (
            [b] => default
        )

)
O:1:"A":2:{s:1:"a";s:10:"serialized";s:1:"b";O:1:"B":1:{s:1:"b";s:10:"serialized";}}A Object
(
    [a] => serialized
    [b] => B Object
        (
            [b] => serialized
        )

)
A Object
(
    [a] => serialized
    [b] => B Object
        (
            [b] => serialized
        )

)