Определить реальный IP-адрес пользователя, выкинуть прокси и взять настоящий IP (если это возможно).

getUserRealIP.php

if (!function_exists('getUserRealIP')) {
    function getUserRealIP() {
        $realIP = null;
        if(isset($_SERVER['HTTP_X_FORWARDED_FOR']) && $_SERVER['HTTP_X_FORWARDED_FOR']) {
            if(strpos($_SERVER['HTTP_X_FORWARDED_FOR'], ".")>0 && strpos($_SERVER['HTTP_X_FORWARDED_FOR'], ",")>=0) {
                $forwardedIPArray = explode(",", $_SERVER['HTTP_X_FORWARDED_FOR']);
                $realIP = trim($forwardedIPArray[0]);
            } elseif (strpos($_SERVER['HTTP_X_FORWARDED_FOR'], ".")>0 && strpos($_SERVER['HTTP_X_FORWARDED_FOR'], ",")===false) {
                $realIP = trim($_SERVER['HTTP_X_FORWARDED_FOR']);
            }
        // RFC 7239 http://tools.ietf.org/html/rfc7239
        } else if (isset($_SERVER['HTTP_FORWARDED']) && $_SERVER['HTTP_FORWARDED'] && strpos($_SERVER['HTTP_FORWARDED'], "for")>=0) {
            $forwardedForArray = explode(",", $_SERVER['HTTP_FORWARDED']);
            $forwardedFor = $forwardedForArray[0];
            $forwardedForArray = explode(";", $forwardedFor);
            $forwardedFor = $forwardedForArray[0];
            if (strpos($_SERVER['HTTP_FORWARDED'], "for")>=0) {
                $forwardedForArray = explode("=", $forwardedFor);
                if (sizeof($forwardedForArray) > 0) {
                    $realIP = trim($forwardedForArray[1]);
                } else {
                    $realIP = $_SERVER['REMOTE_ADDR'];
                }
            } else {
                $realIP = $_SERVER['REMOTE_ADDR'];
            }

        } else {
            $realIP = $_SERVER['REMOTE_ADDR'];
        }
        return $realIP;
    }
}