inventarioSustancias/public_html/header.php

<?php
/*  Authors         :   Carlos C. Corrada-Bravo
                        David J. Ortiz-Rivera

    Organization    :   Centro de Desarrollo y Consultoria Computacional
    Project         :   OPASO Material Registry   
    File            :   header
    Description     :   Handle session expiry for OPASO */

	/* start user session */
	if(!isset($_SESSION)){
		session_start();
	}

	/* check for expired session */
	if(!isset($_SESSION["last_activity"]) or (time() - $_SESSION["last_activity"]) > 1800){
		session_unset();
		session_destroy();
		$_SESSION = array();
		header("Location: /?error=session_expired");
		die();
	}

	/* update last activity */
	else{
		$_SESSION["last_activity"] = time();
	}

	/* update session id, after 30 mins */
	if((time() - $_SESSION["created"]) > 1800){
	    session_regenerate_id(true);
	    $_SESSION["created"] = time();
	}
?>