【PHP】获取用户真实IP

function get_real_ip()
{
    $ip = $_SERVER['REMOTE_ADDR'];

    if (isset($_SERVER['HTTP_CF_CONNECTING_IP']) && preg_match('/^([0-9]{1,3}.){3}[0-9]{1,3}$/', $_SERVER['HTTP_CF_CONNECTING_IP']))
    {
        $ip = $_SERVER['HTTP_CF_CONNECTING_IP'];
    } 
    elseif (isset($_SERVER['HTTP_CLIENT_IP']) && preg_match('/^([0-9]{1,3}.){3}[0-9]{1,3}$/', $_SERVER['HTTP_CLIENT_IP'])) 
    {
        $ip = $_SERVER['HTTP_CLIENT_IP'];
    } 
    elseif(isset($_SERVER['HTTP_X_FORWARDED_FOR']) && preg_match_all('#d{1,3}.d{1,3}.d{1,3}.d{1,3}#s', $_SERVER['HTTP_X_FORWARDED_FOR'], $matches)) 
    {
        foreach ($matches[0] AS $xip) 
        {
            if (!preg_match('#^(10|172.16|192.168).#', $xip)) 
            {
                $ip = $xip;
                break;
            }
        }
    }
    return $ip;
}