Description:
------------
I do not have the same behaviour with or without APC enabled, when handling php shutdown, especially session_set_save_handler.
This only happen when using FastCGI of course :) Maybe it happens with PHP as a module, I did not test it.

First time the script is executed : no error. Second time (and third, ...) : error happened.

For helping you reproduce the bug, here are the command lines used with cgi-fcgi : 

$ cgi-fcgi -start -connect test.sock /usr/bin/php-cgi

Then, call the following command line several times :
$ SCRIPT_FILENAME=bugapc.php cgi-fcgi  -connect test.sock /usr/bin/php-cgi

Reproduce code:
---------------
<?php

class MyTest {
    public function __construct() { }
    public function open () { }
    public function close () { echo __FUNCTION__;}
    public function read () { }
    public function write () { echo __FUNCTION__;}
    public function destroy () { }
    public function gc () { }
}

session_set_save_handler(
    array('MyTest', 'open'),
    array('MyTest', 'close'),
    array('MyTest', 'read'),
    array('MyTest', 'write'),
    array('MyTest', 'destroy'),
    array('MyTest', 'gc')
);
        
session_start();


Expected result:
----------------
First launch (no error) : 
==========
writeclose
==========

Actual result:
--------------
First launch is expected result.

Then : 
==========
Fatal error: Class 'MyTest' not found in Unknown on line 0
Fatal error: Class 'MyTest' not found in Unknown on line 0
==========

=> Error happened when php called MyTest::write() and MyTest::close() internally.