Description:
------------
If I first assigned value by value, the result is correct. But if I first 
assigned value by references, result is very strange. 

<?php
$array2 = array('ooo');
$array2[] =& $array2;
$array2[] = $array2;
xdebug_debug_zval(array2);
?>
Above script will get bellow output:
array2: (refcount=3, is_ref=1)=array (0 => (refcount=2, is_ref=0)='ooo', 1 => 
(refcount=3, is_ref=1)=..., 2 => (refcount=2, is_ref=0)=array (0 => (refcount=2, 
is_ref=0)='ooo', 1 => (refcount=3, is_ref=1)=..., 2 => (refcount=2, 
is_ref=0)=...)) 

but when run at "$array2[] = $array2", $array2[2] now haven't any value, but 
after assigned, it have a circle reference to $array2[2]...
I think this is a bug...
If this is't a bug, could tell me why?

Test script:
---------------
<?php
$array1 = array('ooo');
$array1[] = $array1;
$array1[] =& $array1;
$array2 = array('ooo');
$array2[] =& $array2;
$array2[] = $array2;

print "<h1>Initial datas</h1>";
print <<< 'nowdoc'
$array1 = array('ooo');<br />
$array1[] = $array1;<br />
$array1[] =& $array1;<br />
$array2 = array('ooo');<br />
$array2[] =& $array2;<br />
$array2[] = $array2;<br />
nowdoc;

print "<h1>xdebug_debug_zval result:</h1>";
xdebug_debug_zval("array1"); print "<br />";
xdebug_debug_zval("array2"); print "<br />";
?>