Description:
------------
There is a similar issue here: https://bugs.php.net/bug.php?id=59197 but the last comment seems a bit different, is for another php version, and very similar to my issue, so I believe we may have a different source of our problem.

When calling any page in my Drupal setup, I get:
Fatal error: Class SchemaCache contains 5 abstract methods and must therefore be declared abstract or implement the remaining methods (DrupalCacheArray::resolveCacheMiss, ArrayAccess::offsetExists, ArrayAccess::offsetGet, ...) in /var/www/bootstrap.inc on line 2849

The code is publicly available here: http://drupalcode.org/project/drupal.git/blob/4d4080b17681ae674e10c077b72d00f0b1544e0c:/includes/bootstrap.inc
where it's easy to see that the 5 methods _are_ implemented. Disabling APC solves the issue.

Last comment from 59197 copied in:
I'm seeing a similar issue using APC 3.1.9 with PHP 5.4.0RC4 on Windows (Win7 
x64, Apache 2.2.17). I've built APC myself using VS2008 (shared, TS, x86, 
Release).

After enabling APC, my app crashes randomly with bogus error messages. Sometimes methods in subclasses are not detected:



/lib/Base.php
-------------

class Base {
   abstract protected function foo();
}



/lib/Sub.php
------------

class Sub extends Base {
   protected function foo() { print "world!"; }
}



After including both files, I get "Sub contains abstract methods and must 
therefore also be abstract (Base::foo())". When I restart Apache, the error goes 
away for one request. After that, I get "Call to undefined method 
Loader::addPath" (this method definitely exists, disabling APC makes it work 
again).

My APC config:

-----------------------
apc.enabled = On
apc.cache_by_default = On
apc.slam_defense = 0
apc.write_lock = 1
-----------------------

Expected result:
----------------
I would expect the code to run. :)

Actual result:
--------------
Error message, posted in description.