Description:
------------
The problem is in the different results of isset() in different versions of PHP.
I have tested it with compiled in SPL Support and vithout SPL support; the problem is always the same.

Reproduce code:
---------------
#!/usr/bin/php
<?php

$blah = 'ABC';

var_dump($blah, $blah->foo, isset($blah->foo));

?>

Expected result:
----------------
I get this Result in following versions of PHP:
 - PHP 5.0.0 as Apache Module
 - PHP 5.0.3 as Apache Module
 - PHP 5.0.0 CLI

string(3) "ABC"
NULL
bool(false)


Actual result:
--------------
This is the result in PHP 5.0.3 CLI (With and without SPL support)

string(3) "ABC"
NULL
bool(true)