This is very handy if you want to have a walled garden section inside your private network while still hosting public data.
<?php
$ipcheck = "192.168.0."; //Replace with first 3 octets of your existing IP scheme
if( substr($_SERVER['REMOTE_ADDR'],0,strlen($ipcheck )) == $ipcheck ) {
//Begin Internal code
}else{
//Begin External code
}
?>