Opencarts Maintenance Mode

Hi.

I would like to know if any one knows how open carts back end maintenance mode code work.

I would like to create some thing similar using codeigniter. I use open cart for my store to sell my goods but for my main website I use codeigniter.

Any ideas.

have a look, index.php

where you can find:
// Maintenance Mode
$controller->addPreAction(new Action('common/maintenance'));

Where system check its status first,if its on then it will show relevant
page directly.

Just debug index.php.

What way would you do it for codeigniter?

Add this in index.php

$maintenance = false; ## set to true to enable

if ($maintenance)
{
if (isset( $_SERVER['REMOTE_ADDR']) and $_SERVER['REMOTE_ADDR'] == 'your_ip')
{
##do nothing
} else
{

error_reporting(E_ALL);
ini_set('display_errors', 1); ## to debug your maintenance view

require_once 'maintenance.php'; ## call view
return;
exit();

}
}

==============
and create maintenance.php.