Description:
------------
If ArrayAccess is extended and then the subclass accessed using object notation then unpredicatable results occur. In the test script below an undefined variable $xyz is somehow referencing the ArrayObject subclass Foo.

The same result occurs on Linux systems.

This came to light when using an unitialised value in the Zend Framework Zend_Registry class, although it is not limited to that.

Test script:
---------------
<?php
class Foo extends ArrayObject{
    public function __construct(){
        parent::__construct(array(), parent::ARRAY_AS_PROPS);
    }
}
$f = new Foo;
$f->Foo['bar'] = 1;
var_dump($xyz['xyz']); # This should throw a warning then null??
?>

Expected result:
----------------
PHP Notice:  Undefined index:  Foo in C:\jirasource\ABC\sites\partners.rfp-gener
ator.com\web\test.html.php on line 8
PHP Stack trace:
PHP   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generator.com\web\test.ht
ml.php:0

Notice: Undefined index:  Foo in C:\jirasource\ABC\sites\partners.rfp-generator.
com\web\test.html.php on line 8

Call Stack:
    0.0212      60112   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generat
or.com\web\test.html.php:0

PHP Notice:  Undefined variable: xyz in C:\jirasource\ABC\sites\partners.rfp-gen
erator.com\web\test.html.php on line 9
PHP Stack trace:
PHP   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generator.com\web\test.ht
ml.php:0

Notice: Undefined variable: xyz in C:\jirasource\ABC\sites\partners.rfp-generato
r.com\web\test.html.php on line 9

Call Stack:
    0.0212      60112   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generat
or.com\web\test.html.php:0

PHP Notice:  Undefined index:  xyz in C:\jirasource\ABC\sites\partners.rfp-gener
ator.com\web\test.html.php on line 9
PHP Stack trace:
PHP   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generator.com\web\test.ht
ml.php:0

Notice: Undefined index:  xyz in C:\jirasource\ABC\sites\partners.rfp-generator.
com\web\test.html.php on line 9

Call Stack:
    0.0212      60112   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generat
or.com\web\test.html.php:0

null

Actual result:
--------------
PHP Notice:  Undefined index:  Foo in C:\jirasource\ABC\sites\partners.rfp-gener
ator.com\web\test.html.php on line 8
PHP Stack trace:
PHP   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generator.com\web\test.ht
ml.php:0

Notice: Undefined index:  Foo in C:\jirasource\ABC\sites\partners.rfp-generator.
com\web\test.html.php on line 8

Call Stack:
    0.0212      60112   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generat
or.com\web\test.html.php:0

PHP Notice:  Undefined variable: xyz in C:\jirasource\ABC\sites\partners.rfp-gen
erator.com\web\test.html.php on line 9
PHP Stack trace:
PHP   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generator.com\web\test.ht
ml.php:0

Notice: Undefined variable: xyz in C:\jirasource\ABC\sites\partners.rfp-generato
r.com\web\test.html.php on line 9

Call Stack:
    0.0212      60112   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generat
or.com\web\test.html.php:0

PHP Notice:  Undefined index:  xyz in C:\jirasource\ABC\sites\partners.rfp-gener
ator.com\web\test.html.php on line 9
PHP Stack trace:
PHP   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generator.com\web\test.ht
ml.php:0

Notice: Undefined index:  xyz in C:\jirasource\ABC\sites\partners.rfp-generator.
com\web\test.html.php on line 9

Call Stack:
    0.0212      60112   1. {main}() C:\jirasource\ABC\sites\partners.rfp-generat
or.com\web\test.html.php:0

array(1) {
  ["bar"]=>
  int(1)
}