Fix GC issue when session lifetime is set to 0

* fix #4169 GC processing issues when session lifetime is 0

* Added description about the structure of the session library of the document.

* Apply suggestions from code review

Co-authored-by: John Paul E. Balandan, CPA <51850998+paulbalandan@users.noreply.github.com>

Author: lf-uraku-yuki

system/Session/Session.php

@@ -306,7 +306,7 @@ protected function configure()
 
         if (! isset($this->sessionExpiration)) {
             $this->sessionExpiration = (int) ini_get('session.gc_maxlifetime');
-        } else {
+        } elseif ($this->sessionExpiration > 0) {
             ini_set('session.gc_maxlifetime', (string) $this->sessionExpiration);
         }
 

user_guide_src/source/libraries/sessions.rst

@@ -458,6 +458,12 @@ Preference                     Default                                      Opti
     unexpected results or be changed in the future. Please configure
     everything properly.
 
+.. note:: If ``sessionExpiration`` is set to ``0``, the ``session.gc_maxlifetime``
+    setting set by PHP in session management will be used as-is
+    (often the default value of ``1440``). This needs to be changed in
+    ``php.ini`` or via ``ini_set()`` as needed.
+
+
 In addition to the values above, the cookie and native drivers apply the
 following configuration values shared by the :doc:`IncomingRequest </incoming/incomingrequest>` and
 :doc:`Security <security>` classes: