Accessing object in models parent - php

Question

I am trying to call a function that is inside my Database class but I can't seem to get it right.
My Model class calls Database and assigns it to a variable:
class Model {
function __construct() {
$this->db = new Database();
}
function __destruct() {
$this->db = NULL;
}
}
I'm trying to call it from:
class User extends Controller {
function __construct() {
parent::__construct();
}
public function userExists($username) {
return $this->model->db->select('users', 'id', 'email LIKE ?', array($username));
}
}
But I keep getting the error:
Fatal error: Call to a member function select() on a non-object in C:\Apache24\htdocs\Manager 2014\controllers\User.php on line 10
My Database class is:
class Database extends PDO {
function __construct($user = 'root', $pass = '', $database = 'xxx', $host = 'localhost') {
try {
parent::__construct('mysql:host=' . $host . ';dbname=' . $database, $user, $pass);
$this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);
$this->setAttribute(PDO::ATTR_PERSISTENT, FALSE);
$this->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
$this->setAttribute(PDO::ATTR_EMULATE_PREPARES, FALSE);
$this->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, FALSE);
$this->exec("SET NAMES utf8");
} catch (PDOException $e) {
Database::handleDbError($e);
}
}
public function select($table, $cols, $where = null, $whereVals = null, $order = null) {
if ($this->tableExists($table)) {
$PDOParams = array();
$SQL = 'SELECT ' . $cols . ' FROM ' . $table;
if ($where) {
$SQL .= ' WHERE ' . $where;
}
if ($whereVals) {
}
if ($order) {
$SQL .= 'ORDER BY ' . $order;
}
return $SQL;
} else {
}
}
public function tableExists($table) {
$r = $this->PDO->prepare("SHOW TABLES LIKE ?");
$r->execute(array($table));
return $r->rowCount();
}
}
What am I doing wrong?
If I:
print_r(get_class_vars ('UserModel'));
From the User class I get:
Array( [db] => )
Which doesn't make sense to me because that is being assigned in Model in the constructor that is being called when UserModel is called.
Instead of select() in my Database class, I now have the following in my main Model class:
public function get($primaryKeyId) {
$table = str_replace('model', '', strtolower(get_called_class()));
$SQL = "SELECT * FROM $table WHERE id = ?";
$r = $this->db->prepare($SQL);
$r->execute(array($primaryKeyId));
return $r->fetch();
}

Answer 1

There are many essential flaws with your implementation.
First and foremost, get rid of select() function
it's awfully insecure, allowing raw variables into query
it's fantastically inflexible, allowing only silly sandbox queries
it makes unreadable gibberish out of neat almost natural English of SQL
Second, do not create anew DB instance every time you invoke a class. Even simple app will kill your db server with that much number of connects.
pass db as a parameter into constructor instead
As it seems from your comment, errorhandler method doesn't handle anything which makes it evil
if you have no idea how to handle an error - just let it go. Get rid of this try/catch thingy completely

Answer 2

The database object in your model needs to be public so it can be accessed outside of the Model class.
class Model {
public $db;
function __construct() {
$this->db = new Database();
}
function __destruct() {
$this->db = NULL;
}
}
See object visibility for details on the difference between public, protected, and private.

Answer 3

I had just done a custom build of AMP and forgot to enable mysql PDO extension...That's why the DB parameter was empty FACEPALM.