Description:
------------
Hard to explain, see code... I think that PHP should be able to handle this kind of loading scheme.

Here is what I thought this code would do :
1. __autoload('A') is called
2. inside this call for A:
   2.1 class B is defined, which extends C
   2.2 as C is not defined, __autoload('C') is called
   2.3 inside this call for C:
       2.3.1 class C is defined
       2.3.2 (now we have everything needed for class B, haven't we ?)
       2.3.3 class A extends B
   2.4 we leave the __autoload('C') context
3. we leave the __autoload('A') context

The bug is at step 2.3.3 : "class A extends B" triggers an autoload('B'), which should not occurs, as B should be already defined, thanks to 2.3.2...

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

function __autoload($class)
{
        switch ($class)
        {
        case 'A':
        case 'B':
                class B extends C {};
                break;

        case 'C':
                class C {};
                class A extends B {};
                break;

        }
}

echo (int) class_exists('A');


Expected result:
----------------
1

Actual result:
--------------
Fatal error: Cannot redeclare class B in [...] on line 9