BTW, running PHP_CompatInfo with PHP 5.3.9 on your source code gave me fake negative.
Given that I haven't made any tests, your negative may not be a fake one :-D .
Finally, I fall down in my own ambush ;-)
This is not a fake one, but a fake negative
Little explains :
With your source code "src\PEAR2\Cache\SHM\Adapter\APC.php", running this command
phpci print --report function src\PEAR2\Cache\SHM\Adapter\APC.php
I got first this report
-------------------------------------------------------------------------------
PHP COMPAT INFO FUNCTION SUMMARY
-------------------------------------------------------------------------------
FUNCTION EXTENSION VERSION COUNT
-------------------------------------------------------------------------------
array_search standard 4.0.5 1
microtime standard 5.0.0 2
register_shutdown_function standard 4.0.0 1
apc_add 5.3.0 2
apc_delete 5.3.0 3
apc_exists 5.3.0 2
apc_fetch 5.3.0 1
apc_store 5.3.0 1
-------------------------------------------------------------------------------
A TOTAL OF 8 FUNCTION(S) WERE FOUND
REQUIRED PHP 5.3.0 (MIN)
-------------------------------------------------------------------------------
Which give 5.3.0 for apc functions due to namespace usage in source code, but it's not true (I should load the apc extension)
To give the right result
-------------------------------------------------------------------------------
PHP COMPAT INFO FUNCTION SUMMARY
-------------------------------------------------------------------------------
FUNCTION EXTENSION VERSION COUNT
-------------------------------------------------------------------------------
apc_add apc 4.0.0 2
apc_delete apc 4.0.0 3
apc_exists apc 5.0.0 2
apc_fetch apc 4.0.0 1
apc_store apc 4.0.0 1
array_search standard 4.0.5 1
microtime standard 5.0.0 2
register_shutdown_function standard 4.0.0 1
-------------------------------------------------------------------------------
A TOTAL OF 8 FUNCTION(S) WERE FOUND
REQUIRED PHP 5.0.0 (MIN)
-------------------------------------------------------------------------------
In summary :
If you have extension column empty, either it's really user function, either you don't have loaded extension or specified it in the PHPCI configuration file.
Confused
Laurent