From PhpCOIN Documentation
Normally when a surfer visits your phpCOIN-powered website, they will be greeted with the contents of your Admin -> SiteInfo Pages -> index page.
Occasionally you may want to make your website "unavailable". For example, you do not want a surfer trying to place an order while you are upgrading phpCOIN files, or programming a custom add-on to the orders module.
config.php contains a variable called $_CCFG['_PKG_MODE_OFFLINE'] which is usually set as zero so the web-site operates normally. When set to 1, instead of your normal web-site visitors will see the content of the index_offline.html page. This allows your site to "respond", while you play or make major changes.
But you may need phpCOIN to operate normally for you, even though it is "offline" to everybody else.
config.php contains a variable called $_CCFG['_PKG_MODE_ONLINE_IP'] to help with this situation. When phpCOIN is set as offline, a surfer connecting to the website phpCOIN will see the "offline" page unless their ip address is set in $_CCFG['_PKG_MODE_ONLINE_IP']
The content of $_CCFG['_PKG_MODE_ONLINE_IP'] should be your IP address, and if you use more than one computer to connect to the internet then enter as many of those ip addresses as you need, separated by commas.