Description:
------------
Taking the example (#2) from the documentation page of the isset-function (Example #2 isset() on String Offsets), and modifying the test to contain [0] references somewhere along the array path, you can see, that each of these references provide a 'true' result, despite this is clearly not correct (see attached script), since the first part of the array patch does not exist (so any subsequent path cannot exist either).

Test script:
---------------
<?php
$expected_array_got_string = 'einstring';
var_dump(isset($expected_array_got_string['und']));
var_dump(isset($expected_array_got_string['und'][0]));
var_dump(isset($expected_array_got_string['und'][0]['test']));
var_dump(isset($expected_array_got_string['und']['test'][1]));
var_dump(isset($expected_array_got_string['und']['test'][0]));
?>


Expected result:
----------------
bool(false)
bool(false)
bool(false)
bool(false)
bool(false)


Actual result:
--------------
bool(false)
bool(true)
bool(false)
bool(false)
bool(true)