Stupid quastion about sessions

I have some problem with sessions.

<?
session_start();
$counter++;
session_register("counter");
?>
...
<?
print($counter);
?>

When I see my counter based on sessions. Let's look at my /tmp:
su-2.03# ls /tmp
sess_05f2199423e0c57b45469a0d539e3963
su-2.03#

This file is not deleted any more almost two days URL Though in options of php.ini we could see:

[Session]
session.save_handler = files
session.save_path = /tmp
session.use_cookies = 1
session.name = PHPSESSID
session.auto_start = 0
session.cookie_lifetime = 0
session.cookie_path = /
session.serialize_handler = php
session.gc_probability = 1
session.gc_maxlifetime = 1440
session.entropy_length = 0
session.cache_limiter = nocache
session.cache_expire = 180

What's wrong? Btw, give me url where I could read about sessions (examples)..etc... Please...

Sorry 4 my bad english.
wbr,Dennis.

I think you need to set session.cookie.lifetime to null instead of 0... but i could be wrong as i haven't got experience of using php.ini to set cookie parameters...

No, it doesn't have anything to do with the cookie lifetime. The two relevent lines are:

session.gc_probability = 1
session.gc_maxlifetime = 1440

The maxlifetime is 1440 seconds, but with a probability of only 1 (1%) that means there is only a 1% chance that old sessions will be cleaned up whenever a session_start() is called. Meaning that the overhead of cleanup is limited instead of being done constantly. If you have a low volume website you could increase the probability that cleanup will occur.