Description:
------------
When var_dumping $f it appears a notice message, saying
Warning: array_merge_recursive(): recursion detected in ...
It is kind of strange because as far as I expect it is supposed to be the same result as in the line where $e is being var_dumped. var_dump($e) gives correct result:
array 
  'a' => 
    array 
      0 => 'aa' 
      1 => 'aa' 
  'b' => 
    array 
      0 => 'bb' 
      1 => 'bb'

and var_dump($f) gives notece message and result is 

array 
  'a' => 'aa' 
  'b' => 'bb'

problem appears in 4.3.1 too, but not in 4.2.2

Reproduce code:
---------------
<?php 

$c=array('a' => 'aa','b' => 'bb'); 
$d=array('a' => 'aa','b' => 'bb'); 

$a=$c; 
$b=$c; 

$f=array_merge_recursive($a,$b); 
var_dump($f); 

$e=array_merge_recursive($c,$d); 
var_dump($e); 

?>

Expected result:
----------------
array 
  'a' => 
    array 
      0 => 'aa' 
      1 => 'aa' 
  'b' => 
    array 
      0 => 'bb' 
      1 => 'bb'

array 
  'a' => 
    array 
      0 => 'aa' 
      1 => 'aa' 
  'b' => 
    array 
      0 => 'bb' 
      1 => 'bb'

Actual result:
--------------
Warning: array_merge_recursive(): recursion detected in c:\servak\www\tests\array_merge_recursive.php on line 9

array
  'a' => 'aa'
  'b' => 'bb'

array
  'a' => 
    array
      0 => 'aa'
      1 => 'aa'
  'b' => 
    array
      0 => 'bb'
      1 => 'bb'