safest method to check user ip with cloudflare

check-ip-cloudflare-and-direct.php

<?php

function _getUserRealIP() {
    $ipaddress = '';
    if(isset($_SERVER['REMOTE_ADDR']))
        $ipaddress = $_SERVER['REMOTE_ADDR'];
    else
        $ipaddress = 'UNKNOWN';
    return $ipaddress;
}

function _readCloudflareIps()
{
    $file = file("https://www.cloudflare.com/ips-v4",FILE_IGNORE_NEW_LINES);
    return $file;
}

function _checkIpInRange($ip, $range) {
    if (strpos($range, '/') == false)
        $range .= '/32';

    // $range is in IP/CIDR format eg 127.0.0.1/24
    list($range, $netmask) = explode('/', $range, 2);
    $range_decimal = ip2long($range);
    $ip_decimal = ip2long($ip);
    $wildcard_decimal = pow(2, (32 - $netmask)) - 1;
    $netmask_decimal = ~ $wildcard_decimal;
    return (($ip_decimal & $netmask_decimal) == ($range_decimal & $netmask_decimal));
}

function _checkIsCloudflare($ip) {
    $cf_ips = _readCloudflareIps();
    $is_cf_ip = false;
    foreach ($cf_ips as $cf_ip) {
        if (_checkIpInRange($ip, $cf_ip)) {
            $is_cf_ip = true;
            break;
        }
    }
    return $is_cf_ip;
}

function getRealIp()
{
    $httpIp = _getUserRealIP();
    $check = _checkIsCloudflare($httpIp);
    if ($check) {
        return $_SERVER['HTTP_CF_CONNECTING_IP'];
    }else{
        return $httpIp;
    }
}