note 86138 added to function.isset

It has been remarked by various people that isset is the opposite of is_null "in all but buggy cases". This is not true:

<?php
  $str = "hi";
  var_dump(isset($str[1]));
  var_dump(@!is_null($str[1]));
  var_dump(isset($str[2]));
  var_dump(@!is_null($str[2]));
?>

outputs

bool(true)
bool(true)
bool(false)
bool(true)
----
Server IP: 212.108.64.191
Probable Submitter: 89.100.142.134
----
Manual Page -- http://www.php.net/manual/en/function.isset.php
Edit        -- https://master.php.net/note/edit/86138
Del: integrated  -- https://master.php.net/note/delete/86138/integrated
Del: useless     -- https://master.php.net/note/delete/86138/useless
Del: bad code    -- https://master.php.net/note/delete/86138/bad+code
Del: spam        -- https://master.php.net/note/delete/86138/spam
Del: non-english -- https://master.php.net/note/delete/86138/non-english
Del: in docs     -- https://master.php.net/note/delete/86138/in+docs
Del: other reasons-- https://master.php.net/note/delete/86138
Reject      -- https://master.php.net/note/reject/86138
Search      -- https://master.php.net/manage/user-notes.php