Description:
------------
Various results empty() for nonexistent key 

Reproduce code:
---------------
$w=array('a'=>'aaaa','b'=>array('dd'=>1,'aa'=>2));

foreach($w as $k=>$v)
{
        if(empty($v['dd']))
                echo "{$k}:empty<br>\n";
        else
                echo "{$k}:no empty<br>\n";
}


Expected result:
----------------
a:empty<br>  
b:no empty<br>

(PHP 5.03 FreeBsd 4.9)

Actual result:
--------------
a:no empty<br>  
b:no empty<br>

(PHP 5.05 FreeBsd 5.3)