The session related settings of config.php are set as follows.

$config ['sess_cookie_name'] = 'ci_session';
$config ['sess_expiration'] = 10;

[Local environment]
Session ID is set in $_COOKIE ['ci_session'],
Session expires in 10 seconds.

[Production environment (rental server)]
Session ID is set to $_COOKIE ['PHPSESSID']
The session continues until you close the browser.
($_COOKIE ['ci_session'] does not exist.)

I'd be happy if you could tell me what this difference in behavior is.

~ Supplement ~
in system \ libraries \ Session \ Session.php
It seems that the behavior switches, but it was difficult to track the code. I gave up and decided to ask a question here.

Thanks for your cooperation.