Description:
------------
php-5.5.0alpha5-nts-Win32-VC11-x86

PHP 5.5.0alpha5 (cli) (built: Feb 21 2013 17:11:43)
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.5.0-dev, Copyright (c) 1998-2013 Zend Technologies
    with Zend Optimizer+ v7.0.0, Copyright (c) 1999-2013, by Zend Technologies

There is a strange issue with Optimizer+ when some loaded classes can "disappear". It's related to the dynamic includes and filter system. 
Go! AOP library uses this technique to perform "monkey-patching" before PHP parser.

Test script:
---------------
https://gist.github.com/lisachenko/00fa92f811511f347e3a

// bug.php
<?php
class BugLoader extends php_user_filter
{

    public function filter($in, $out, &$consumed, $closing)
    {
        eval("class Test extends ArrayObject {}");
        return PSFS_PASS_ON;
    }
}

function dynamicInclude()
{
    return "php://filter/read=bug.test/resource=test.php";
}
echo "ArrayObject class ", class_exists('ArrayObject') ? 'exists' : 'not found';
stream_filter_register('bug.test', 'BugLoader');
include dynamicInclude();

//test.php
<?php
// Empty file here

Expected result:
----------------
ArrayObject class exists

Actual result:
--------------
ArrayObject class exists
Fatal error: Class 'ArrayObject' not found in ~/bug.php(7) : eval()'d code on line 1