Another option is to insert some test code, either into the PHP code or possibly at the web server level, in order to insert test IP values. Something real simple would be:
<?php
define('IPTEST', true); // change to false for live version
if(is_defined('IPTEST') and IPTEST == true)
{
if(is_readable('ip.txt'))
{
$_SERVER['REMOTE_ADDR'] = trim(file_get_contents('ip.txt'));
}
}
// rest of script
?>
Then just edit ip.txt to contain whatever IP address you want to test, and ensure the define() statement is there and setting IPTEST to true. (You could then either set it to false or just comment it out when in "live" mode.)