Description:
------------
using isset() to detect the existence of array subkeys give a false positive.  Also, trying to print the content of said non-existing keys gives the first character of the parent key!

Reproduce code:
---------------
$aArray = array();
$aArray["key"] = "value";
print("<PRE>".print_r($aArray, true)."</PRE>");
if (isset($aArray))
	print("Array exists<BR>");
else print("Array does not exist.<BR>");
if (isset($aArray["key"]))
	print("Array[key] exists, value = '".$aArray["key"]."'<BR>");
else print("Array[key] does not exist.<BR>");
if (isset($aArray["key"]["subkey"]))
	print("Array[key][subkey] exists, value = '".$aArray["key"]["subkey"]."'<BR>");
else print("Array[key][subkey] does not exist.<BR>");


Expected result:
----------------
Array
(
    [key] => value
)

Array exists
Array[key] exists, value = 'value'
Array[key][subkey] does not exist

Actual result:
--------------
Array
(
    [key] => value
)

Array exists
Array[key] exists, value = 'value'
Array[key][subkey] exists, value = 'v'