Resolve real public clients ip address behind reverse proxy

// Function that decides to return as remote address the HTTP_X_FORWARDED_FOR (if exists) for cases of reverse proxy
function Actual_REMOTE_ADDR()
{
    // DEFINE HERE THE IP ADDRESSE(s) OF REVERSE PROXY(s)
    $reverse_proxy_addresses = array('15.14.13.1');

    $client_address = $_SERVER['REMOTE_ADDR'];

    // Check if resolved REMOTE_ADDR is one of the reverse proxy address
    $revpr_found = in_array($client_address, $reverse_proxy_addresses);

    // If so, try to get the HTTP_X_FORWARDED_FOR value of the request's header
    if($revpr_found)
    {
        if(isset($_SERVER['HTTP_X_FORWARDED_FOR']) && $_SERVER['HTTP_X_FORWARDED_FOR'] !== "")
        {
            $client_address = $_SERVER['HTTP_X_FORWARDED_FOR'];
            $client_arr = explode(",", $client_address);

            // It happens, for some networks, if app is behind reverse proxy, $client_address to have 2 values
            // Must get the first one only
            if(count($client_arr) > 1)
                $client_address = $client_arr[0];
        }
    }

    return $client_address;
}