PHP Module unload

Hello experts,

I have a question on PHP module unloading. We are using PHP 5.3.2
on BSD. We are looking to use PHP as a module with APC cache due to
performance reasons. I have limited APC memory to 8mb.

The memory usage with PHP module is obviously persistent compared
to CGI. We have a embedded device environment so we want to limit
memory usage to a minimum since the web access to the device is used infrequently.

Is there a feature in PHP either via php.ini or code change where we
can unload the PHP module after a certain time be it eg no sessions/activity
for a certain time.

I searched through the lists and did not find much.

Thanks