Worth to mention the result of test.php execution in APC 3.1.3p1, PHP 5.3.3:
1 0
0
0
0
0
...

Issue with duplicate variables not repeating in this case.

I'm seeing the same problem here, too, on two different Fedora 13 64-bit test servers with PHP 5.3.3. It's occurring with 3.1.4 from the fedora repository, as well as any copy which I compile myself. It doesn't seem to matter what combination of compiler options I pick or whether I'm using IPC or shared memory.

I'm having to keep my production server on 5.2.10 for now.

Seeing same problem with key duplication after upgrading our development server to PHP 5.3.3 and APC 3.1.4 .  

Have 2 other servers of identical hardware and OS (Centos 4), PHP 5.2.13 and APC 3.1.3p1 and problem doesn't exist there.

There seems to be another problem that seems to be hinted above - apc_store() is storing a 'false' value, usually after the user cache has been cleared.

Even more frustrating, it seems to be intermittent, but can be reproduced by doing:

apc_store('foo', 'bar', 3600);

then:
                              
apc_clear_cache('user');

and again:

apc_store('foo', 'bar', 3600);

Running into this too, it seems like there are issues with key names being different during store / retrieve operations. The key names look identical but I suspect that this change:

Bug #17978: standardize user keys to include NULs in identifier_len. Z_STRLEN_P() doesn't, so add to it.

Is the real cause of these issues. It seems some functions are not taking this new possibility of embedded NUL into account when comparing key names?

I have this issue also with APC 3.1.4 - PHP 5.3.3

I found this bug report because I was looking to see if anyone has the answer to this problem. All I can do is to add "me too" to this thread. Using php 5.3.3 with APC 3.1.4
I have 2 different server setups: once Apache with mod_php and another one is Lighttpd with php-fpm based factcgi.
Both of these setups have duplicate entry issues. I am using APC only to cache php classes, not using it to cache anything by keys, I have memcache for that.

Example:
[3] => Array
                (
                    [filename] => /usr/local/apache/sites/apacheserver/htdocs/!inc.php
                    [device] => 2051
                    [inode] => 37686147
                    [type] => file
                    [num_hits] => 3
                    [mtime] => 1288646012
                    [creation_time] => 1288646047
                    [deletion_time] => 0
                    [access_time] => 1288646140
                    [ref_count] => 0
                    [mem_size] => 119112
                )

            [4] => Array
                (
                    [filename] => /usr/local/apache/sites/apacheserver/htdocs/!inc.php
                    [device] => 2051
                    [inode] => 37686145
                    [type] => file
                    [num_hits] => 1
                    [mtime] => 1288641935
                    [creation_time] => 1288642030
                    [deletion_time] => 0
                    [access_time] => 1288642032
                    [ref_count] => 0
                    [mem_size] => 114984
                )

            [5] => Array
                (
                    [filename] => /usr/local/apache/sites/apacheserver/htdocs/www/index.php
                    [device] => 2051
                    [inode] => 37686144
                    [type] => file
                    [num_hits] => 3
                    [mtime] => 1288643813
                    [creation_time] => 1288646047
                    [deletion_time] => 0
                    [access_time] => 1288646140
                    [ref_count] => 0
                    [mem_size] => 28840
                )

            [6] => Array
                (
                    [filename] => /usr/local/apache/sites/apacheserver/htdocs/www/index.php
                    [device] => 2051
                    [inode] => 37686143
                    [type] => file
                    [num_hits] => 0
                    [mtime] => 1288640054
                    [creation_time] => 1288640063
                    [deletion_time] => 0
                    [access_time] => 1288640063
                    [ref_count] => 0
                    [mem_size] => 28840
                )

Please try using 3.1.5

@d.snytkine:

Please note that php files appearing in the cache multiple times is perfectly normal.

From what i can see all four instances of index.php have different inode numbers. There is no way to figure out what was the original inode number for a file that's already been changed, so it cannot be selectively deleted easily.

That is not a bug.

As for the rest, I can't reproduce it at all with 3.1.5.

I upgraded to 3.1.5 and this problem is still persist and even 
I got more apache crashes. Fortunately it seems that the 
problem has been fixed in 3.1.6dev 
http://downloads.php.net/pierre/php_apc-3.1-svn20101116-5.3-
vc6-x86.zip

Thank you very much

Hy I have a APC (3.1.5-dev) version installed on a  PHP Version 5.3.2-1ubuntu4.2

And i have this same damn problem.... since i updated to this version i get it even more often.... earlier i used apc 3.1.4 and almost never had this issue but now i have the damn thing after 100 tries.... and after i try to store a  different variable then it works... but after i clear the cache  the first variable wont be stored 100%!!!!

We are also experiencing this issue after upgrading to 
php5.3.3 with APC 3.1.4 on FreeBSD 7.2 and 8.1. We have 
several servers running this setup and this bug is affecting 
them all. Ca anyone confirm/deny if 3.1.5 fixes this as there 
are conflicting reports and its not available in the FreeBSD 
port tree yet

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