Description:
------------
If a global array is assigned to a local variable as in the example, and the local variable is iterated afterwards, the key() function changed the behaviour in the global scope with PHP 5.2.1.

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

function foo()
{
	global $arr;
	
	$c = $arr["v"];
	foreach ($c as $v) {}
}

$arr["v"] = array("a");

echo "-".key($arr["v"])."-";	// prints "0"
foo();
echo "<br/>-".key($arr["v"])."-";	// prints "" since 5.2.1 ("0" on all prior versions)


?>

Expected result:
----------------
-0-
-0-

Actual result:
--------------
-0-
--