<?php
session_start();

define('SYS', $_SERVER['DOCUMENT_ROOT'].'/system/');

class DB
{
    private $link;
    private $host = 'localhost';
    private $user = 'root';
    private $password = '';
    private $database = 'test5';
    private $table = 'users';

    // Подключаемся к базе
    public function __construct()
    {
        $this->link = mysqli_connect($this->host, $this->user, $this->password, $this->database);
    }

    // Делаем запрос к базе
    public function get($id, $field)
    {
        $query = $this->createSelect($id, $field);
        $result = $this->makeQuery($query);
        return $result[$field];
    }

    // Создаем строку с запросом
    private function createSelect($id, $field)
    {
        $table = $this->table;
        return "SELECT $field FROM $table WHERE id=$id";
    }

    // Совершаем запрос к базе
    private function makeQuery($query)
    {
        $result = mysqli_query($this->link, $query);
        return mysqli_fetch_assoc($result);
    }
}

class User
	{
        private $id;
        private $db;

        public function __construct($id)
        {
            $this->id = $id;

            // Создаем объект для работы с БД
            $this->db = new DB;
        }

        public function getName()
        {
            return $this->db->get($this->id, 'name');
        }

        public function getAge()
        {
            return $this->db->get($this->id, 'age');
        }

	}
?>