class DB
{
    private static $_instance;
    private $pdo;

    private $dbUser = 'hellomoto';
    private $dbPassword = 'pass';
    private $dbName = 'training';
    private $dbHost = 'localhost';

    private function __construct() {
        try {
            $h = new PDO("mysql:host=$this->dbHost;dbname=$this->dbName", $this->dbUser, $this->dbPassword);
        } catch (PDOExeption $e) {
            die($e->getMessage());
        }
        $this->pdo = $h;
    }

    static protected function getInstance() {
        if (self::$_instance === null) {
            self::$_instance = new self();
        }
        return self::$_instance;
    }

    private function __clone() {}
    private function __wakeup() {}

    public function Select($query) {
        $stmt = $this->pdo->query($query);
        $result = $stmt->fetch(PDO::FETCH_ASSOC);
        return $result;
    }

}

class ArticlesModel extends DB
{

    private static $_instance;
    private $msql;

    static public function getInstance() {
        if (self::$_instance === null) {
            self::$_instance = new self();
        }
        return self::$_instance;
    }

    public function __construct() {
        $this->msql = DB::getInstance();
    }

    public function articlesAll() {
        $query = "SELECT * FROM Articles";
        $result = $this->msql->Select($query);
        return $result;
    }
}

$art = ArticlesModel::getInstance()->articlesAll();