The below note is an excellent example of how to 'reset' the session expiration time upon a page refresh.
However, take care to compensate for when the session expires and doesn't renew itself (a bug I believe). If the below example is run every time a script is executed, it will give an 'Undefined index <session name> error' after the session fails to renew. Precede it with and if isset() condition.
<?php
private function startSession($time = 3600, $ses = 'MYSES') {
session_set_cookie_params($time);
session_name($ses);
session_start();
if (isset($_COOKIE[$ses]))
setcookie($ses, $_COOKIE[$ses], time() + $time, "/");
}
?>
The above example states that a session will last an hour without a page refresh until it is scrapped. Upon a page refresh, the expiration time is reset back to one hour again. If you wish to give users the option of 'staying logged in forever', just feed startSession a value of '99999999', which should last about 3 years.