Errors while trying to load data from MySql - php

Question

I am working/learning how to mvc a project structure. I have a database connector, a registry class, a model and an application model. I have all these in one place to check it working. The problem is I get these three errors when I execute.
<?php
class db
{
protected $conn;
protected $host, $username, $password, $database;
public function __construct($host, $username, $password, $database)
{
$this->conn = new mysqli($host, $username, $password, $database)
OR die("There was a problem connecting to the database");
return true;
}
public function query($sql)
{
$result = $this->conn->query($sql);
if (!$result) {
die('Invalid query:');
}
return $result;
}
public function escape($value)
{
return $this->conn->real_escape_string($value);
}
public function countAffected()
{
return $this->conn->affected_rows;
}
public function getLastId()
{
return $this->conn->insert_id;
}
public function __destruct()
{
$this->conn->close()
OR die("Problem disconnecting from the database");
}
}
final class registry
{
private $data = array();
public function get($key)
{
return (isset($this->data[$key]) ? $this->data[$key] : null);
}
public function set($key, $value)
{
$this->data[$key] = $value;
}
public function has($key)
{
return isset($this->data[$key]);
}
}
abstract class Model
{
protected $registry;
public function __construct($registry)
{
$this->registry = $registry; // Undefined variable: registry
}
public function __get($key)
{
return $this->registry->get($key);
}
public function __set($key, $value)
{
$this->registry->set($key, $value);
}
}
class MemberModel extends Model
{
public function getMember()
{
$result = $this->query("SELECT * FROM members"); //Call to undefined method MemberModel::query()
return $result;
}
}
// DB
define('DB_HOSTNAME', 'localhost');
define('DB_USERNAME', 'root');
define('DB_PASSWORD', '');
define('DB_DATABASE', 'pcaframework');
$registry = new registry();
// Database
$db = new db(DB_HOSTNAME, DB_USERNAME, DB_PASSWORD, DB_DATABASE);
$registry->set('db', $db);
$membermodel = new MemberModel(); //Missing argument 1 for Model::__construct()
$allMembers = $membermodel->getMember();
while ($row = mysqli_fetch_assoc($allMembers)) {
echo "First Name: " . $row['name'] . "<br />";
echo "Last Name: " . $row['email'] . "<br />";
echo "<hr />";
}
Missing argument 1 for Model::__construct(), called on $membermodel = new MemberModel();
Undefined variable: registry
Call to undefined method MemberModel::query()
I have commented the error in the code to mark exactly where the error occurs.

Answer 1

Solution to:
$result = $this->query("SELECT * FROM members"); //Call to undefined method MemberModel::query()
Replace with:
$result = $this->conn->query("SELECT * FROM members");
You just forget the "->conn->".
Solution to:
$this->registry = $registry; // Undefined variable: registry
And
$membermodel = new MemberModel(); //Missing argument 1 for Model::__construct()
Just replace this last with the $registry var as a parameter to the new class:
$membermodel = new MemberModel($registry);
You're calling the constructor, that needs a parameter, but you're not refering that parameter.