gistfile1.txt

<?php

if (!in_array(@$_SERVER['REMOTE_ADDR'], array(
    '127.0.0.1',
    '::1',
))) {
    header('HTTP/1.0 403 Forbidden');
    exit('You are not allowed to access this file.');
}

opcache_reset();

?>

<?php

if (isset($_SERVER['REMOTE_ADDR']) && in_array($_SERVER['REMOTE_ADDR'], array(
    '127.0.0.1',
    '::1',
    )
        opcache_reset();
        exit;
)) {
}

header('HTTP/1.0 403 Forbidden');
exit('You are not allowed to access this file.');

<?php

if (!isset($_SERVER['REMOTE_ADDR']) || !in_array($_SERVER['REMOTE_ADDR'], array(
    '127.0.0.1',
    '::1',
    )
)) {
    header('HTTP/1.0 403 Forbidden');
    exit('You are not allowed to access this file.');
}

opcache_reset();

Else people would get access when they don't have a IP address at all :-)