Magento 1 : Skip Maintenance Flag with IP address filters

skip-maintenance-flag-index.php

/* Start - Add these to index.php */
if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
    $ip = $_SERVER['HTTP_CLIENT_IP'];
} elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
    $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
} else {
    $ip = $_SERVER['REMOTE_ADDR'];
}
$allowed = array('188.39.236.202','127.0.0.1');
/* End - Add these to index.php */

/* Modify the maintenance file */
//if (file_exists($maintenanceFile)) {
if (file_exists($maintenanceFile) && !in_array($ip, $allowed)) {
    include_once dirname(__FILE__) . '/errors/503.php';
    exit;
}