class ConnectioUtil {
    $servername = "localhost";
    $username = "username";
    $password = "password";
    $dbname = "myDB";

    function getConnection() {
        return new mysqli($servername, $username, $password, $dbname);
    }
}

class User {
    $login;
    $password;
    // getters, setters
}

class UserDao {
    function getUserByLoginAndPassword($login, $password) {
        $connection = ConnectionUtil.getConnection();
        $sql = "SELECT * FROM user WHERE login = ? AND password = ?;
        $result = $connection->query($sql);
        // create user object from result
        return $user;
    }
}

class UserController {
    // if url path == "http://sitename/login";
    $user = UserDao.getUserByLoginAndPassword(request.getAttribute("login"), request.getAttribute("password"));
    if ($user == null) {
        // not found in db
        // redirect to login.html with error attribute
    } else {
        // user exists in db
        //redirect to main.html
    }
}