Working with Multiple Classes

[gkent]

I apologize in advance if this question has a simple answer. I have had basic PHP programming experience for several years now; however, I have never ventured into object-oriented programming until now. I am trying to learn OOP and rebuild my website using various classes and objects. I can't seem to get beyond this initial problem of utilizing functions of classes from within other classes. Prior to writing on the forum, I referenced this thread (http://www.killersites.com/community/index.php?/topic/5770-new-to-oop-simple-question/) The goal is to create two files -- one (database.php) with all of the functions related to creation, manipulation, etc of databases, and the other (authentication.php) with functions related to user authentication and database confirmation. I would like to be able to call the database.php functions from within the authentication.php file. All of this would be done behind-the-scenes from my view file (login.php - or similar file). I am also using MDB2 from Pear for database connection framework utilizing mysqli.

 

I tried to accomplish what was shared in the instructions; however, I am continuing to receive a fatal error (Fatal error: Call to a member function query() on a non-object). Here is the code from each of the pages.

 

Login.php

global $core;
require_once "functions/core.php";
$core = new Core();

//Intialize Database Connection
$core->db->do_connect();

//Deploy Authentication Class
$core->auth->Authenticate($username, $password);

 

Core.php

require_once 'database.php';
require_once 'authentication.php';

class Core {

public $db;
public $auth;

function __construct() {
	$this->db = new Database();
	$this->auth = new Authentication();	
}

}

 

Database.php

 

class Database {

//Create Variables
private $dbuser;
private $dbpwd;
private $dbhost;
private $dbname;

public $con;

//Construct MySQL_class
public function __construct() {
	;
 	}

public function do_connect() {

	//Setup Connection to MySQL Database
	$dbuser 	= 	"my-username-here";
	$dbpwd	=	"my-password-here";
	$dbhost 	= 	"my-host-here";
	$dbname	=	"my-databasename-here";

	//Include Required Files for PEAR MDB2
	require_once 'MDB2.php';

	//Intialize Database Connection
	$dsn		=	"mysqli://$dbuser:$dbpwd@$dbhost/$dbname";
	$options	=	array("persistent" => true);

	$con 		=&	MDB2::factory($dsn, $options);
	$con->setFetchMode(MDB2_FETCHMODE_ASSOC);

}

public function query($sql) {
	//Will eventually query database... no code written yet.
}

}

 

Authentication.php

 

class Authentication {

//Construct Authentication Class
function __construct()
{
  global $core;

}

//Primary Function (to be called by login script)
function Authenticate($username, $password) {

	//Check whether user exists in the database
	$this->UserExist($username);

	//Validate user's password with the database
	$this->PasswordMatch($username, $password);

}

function UserExist($username) {

	$sql	=	"SELECT * FROM tblUsers WHERE user_login = '$username' LIMIT 1";  //Code works to this point
	$core->db->query($sql); //This is what prompts the error.

}

function PasswordMatch($username, $password) {
		//No code written yet.  Will be similar to UserExist
}

}

 

Any help would be greatly appreciated!