Handling redirection when session timeout via ajax - php

Question

I have a view function which only logged in user can see. When clicking the view button, it will send an ajax request to PHP function and return back the result which then be displayed in the html. The issue is, if the user idle for too long, when they suddenly come and click the view button again, the display (where the ajax response supposed to be displayed) will show the login page instead of the requested data.
It was because the PHP session has expired. I want to prompt an alert to tell them about this timeout session and redirect them to the login page instead but I don't know how to do that cause I tried to console.log() the PHP session and it's still showing all of the session. I am convinced that this is something like a memory or a flash cache (not very sure).
QuickView = (pc_no) =>{
$.ajax({
type: 'get',
url: '<?= $ajax_url; ?>view-receipt/'+pc_no,
data: { pc_no:pc_no },
success: function(res){
console.log(<?= json_encode($this->session->userLogged); ?>)
<?php if($this->session->userLogged){ ?>
$('#receipt-inline-view').html(res);
<?php } else { ?>
if(alert('Your session has expired. Please re-login.')){
window.location.href = '<?= base_url(); ?>';
}
<?php } ?>
}
})
}
Based on the code above, the user session will be stored in $this->session->userLogged. After PHP timeout, it should be cleared. But from console at ajax there, it's still showing the session even after it gets cleared up. Hence, the redirection also cannot be triggered.