php获得客户端真实ip

// 获取客户端IP地址function get_client_ip() {    static $ip = NULL;    if ($ip !== NULL) return $ip;    if (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {        $arr = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);        $pos =  array_search('unknown',$arr);        if(false !== $pos) unset($arr[$pos]);        $ip   =  trim($arr[0]);    }elseif (isset($_SERVER['HTTP_CLIENT_IP'])) {        $ip = $_SERVER['HTTP_CLIENT_IP'];    }elseif (isset($_SERVER['REMOTE_ADDR'])) {        $ip = $_SERVER['REMOTE_ADDR'];    }    // IP地址合法验证    $ip = (false !== ip2long($ip)) ? $ip : '0.0.0.0';    return $ip;}