Description:
------------
We encountered a problem, after reinstalling a pkg with yum, there will be a lot 
of errors:
[Thu Dec 20 16:37:31 2012] [error] [client xxxxx] PHP Fatal error:  Class 
'YCL_Pay' not found in /xxx.php on line 141 

i found that there are two files have same mtime, and in the same directory.

after reinstalling the pkg, the inode changed while mtime not.

apc use devid + inode as the file cache key in system cache, then check mtime to 
see if the file is changed.

Coincidentally，another file 's inode after reinstall is same as the YCL_Pay.php 
's inode before, so the apc fetch the wrong cache entry.

so i add the filesize check in apc_cache_find_slot function to avoid this 
problem.

Test script:
---------------
<?php

/*
* file: test.php
* first run: php -S 127.0.0.1:10090
* then double wget the file.
*  wget 'http://127.0.0.1:10090/test.php' && wget 'http://127.0.0.1:10090/test.php'
*/

$A = '<' . '?php class A{}';
$B = '<' . '?php class B{}';

$t = strtotime("2012-12-21 00:00:00");

file_put_contents('A.php', $A);
file_put_contents('B.php', $B);

// make sure the same mtime
touch ('A.php', $t);
touch ('B.php', $t);

include 'B.php';
include 'A.php';

// use a.php 's inode instead of B.php's
copy('A.php', 'A.php.bak');
copy('B.php', 'A.php');
rename('A.php', 'B.php');
rename("A.php.bak", 'A.php');

// make sure the same mtime
touch ('A.php', $t);
touch ('B.php', $t);