Description:
------------
I have one object with property "myclass1", referenced to second object. And property "myclass2" of second object, referenced to first object.
When I serialize the first object and unserialize the result string, I get three objects: two copies of first object and a copy of second object. 

Reproduce code:
---------------
<?php
  class MyClass1
    { public $myclass2; 
      public $number;
    }

  class MyClass2
    { public $myclass1;
    }

  $a = new MyClass1;
  $a->number = 1;
  $a->myclass2 = new MyClass2;
  $a->myclass2->myclass1 = $a;

  $b = unserialize(serialize($a));
  $b->number = 2;
  echo $b->number;
  echo "\n"; 
  echo $b->myclass2->myclass1->number;
?>


Expected result:
----------------
If serialization was made correctly, then we would get that 
$b and $b->myclass2->myclass1 are references to one instance, and the output of script must be:

2
2


Actual result:
--------------
The actual output is

2
1

this means, that $b and $b->myclass2->myclass1 aren't references to the same instance