jQuery idleNotice Widget 1.0-pre by Jacob Morrison
http://projects.ofjacob.com

 Licensed under the MIT license:
   http://www.opensource.org/licenses/mit-license.php

Example usage (client script):

Only loadTime and expireTime is required. If stayActiveAjax.url isn't set, the stay active functionality won't work.

$(document).idleNotice({
		'loadTime': null,		/* Server's unix time at page load (ex: <?php echo time(); ?>) */
    	'expireTime': null,		/* Unix time (server) until expiration (ex: <?php echo time() + ini_get('session.gc_maxlifetime'); ?>) */
    	'expireWarning': 60, 	/* Seconds to warn before expiration */
    	'stayActiveAjax': {
			'url': "/keep_active.php",    	/* URL to ping to keep session active */
			'notify': true,
			'notifyMessage': 'Attempting to keep session...',
    	},
    	'onExpire': null,		/* What to do when session expires */
    	'warningDialog': {
    		'title': 'Session Expiration Notice',
    		'modal': true, 
    		'width': '400px', 
    		'position': 'top',
    		'draggable': false,
    		'resizable': false,
    		'content': "You will be logged out in #{time}. Do you want to stay logged in and continue on this screen?",		/* Notice to show before expiration */
    		'buttons': {
    			'Stay Logged In': function() { $(document).trigger("stayActive"); }
    		}
    	},
    	'expiredDialog': {
    		'title': 'Session Has Expired',
    		'modal': true, 
    		'width': '400px', 
    		'position': 'top',
    		'draggable': false,
    		'resizable': false,
    		'content': "You have been logged out due to inactivity.",		/* Notice to show before expiration */
    		'buttons': {
    			'Log Back In': "function() { window.location.reload(); }"
    		},
    	}});
    	
Example usage (server script, PHP):
<?php
// in case it hasn't been started
session_start();
$json_return = array(
	'success' => 1,
	'current' => time(),
	'expire' => time() + ini_get('session.gc_maxlifetime')
);

echo json_encode($json_return);exit;
?>