Description:
------------
Returning by reference in a function or method
modify the array if the key asked does not exist

Reproduce code:
---------------
$a=array('x'=>1,'y'=>2);
function & getZ(){
	global $a;
	return $a['z'];
}
function & getT(&$a){
	return $a['t'];
}
function & get4(&$a){
	return $a[4];
}
getZ();
print_r($a);
getT($a);
print_r($a);
get4($a);
print_r($a);


Expected result:
----------------
Array
(
    [x] => 1
    [y] => 2
)
Array
(
    [x] => 1
    [y] => 2
)
Array
(
    [x] => 1
    [y] => 2
)


Actual result:
--------------
Array
(
    [x] => 1
    [y] => 2
    [z] =>     // NULL
)
Array
(
    [x] => 1
    [y] => 2
    [z] =>     // NULL
    [t] =>     // NULL
)
Array
(
    [x] => 1
    [y] => 2
    [z] =>     // NULL
    [t] =>     // NULL
    [4] =>     // NULL
)