<?php
session_start();
$a = new App;
    $a->newUser('xantiv');
    $id = $a->getUid('xantiv');
    foreach ($id as $r) {
        $sid = $r['u_id'];
    }
    $_SESSION['user'] = $sid;
    $_SESSION['do_kogo'] = $sid;

class Core {
    
        protected $db, $result, $prepared;
        private $rows;

        public function __construct () {
            $this->db = new PDO("mysql:host=localhost;dbname=dbb", "user", "pass");
        }

        
        public function query ($sql) {
            $this->result = $this->db->query($sql);
        }

        
        public function rows () {
            $this->rows = $this->result->fetchAll(PDO::FETCH_ASSOC);
            return $this->rows;
        }

    }
class App extends Core {

        public function getUid ($username) {
            $this->query("SELECT u_id FROM Users WHERE Username='$username' LIMIT 1");
            return $this->rows();
        }

        public function newUser ($username) {
            $this->query("INSERT INTO Users (Username) VALUES ('$username')");
        }
        
        // pobieranie wiadomosci z bazy
        public function fetchMessages () {
            $this->query("
                SELECT
                        `Messages`.`Message`,
                        `users`.`username`,
                        `users`.`u_id`    
                FROM    `Messages`
                JOIN     `users`
                ON         `Messages`.`u_id` = `users`.`u_id`
                ORDER BY `Messages`.`time`
                ASC
            ");
            return $this->rows();
        }
        
        
        public function insertMessage ($u_id, $message,$do_kogo) {
            $this->query("INSERT INTO Messages (u_id, Message, time,do_kogo)
                VALUES ($u_id, '$message', NOW(),'$do_kogo')");
        }

    }
?>