Question

I have several classes in an application that I am currently building, and I want to have one access some of the other’s member functions but i can’t seem to do it.

The first class is called MySQLDB:

class MySQLDB{
public $connection;

function __construct(){
//connects to database
}

function login($username, $password){
//queries database...
}
}

Then I have a class called Session:

class Session{
//variables
//constructor

function processlogin($username, $password){
$database->login($username, $password);
}

Then after this I have two class declarations:

$database = new MySQLDB();
$session = new Session();

No matter where i put these statements in relation to the classes I still get the same error:

PHP Notice:  Undefined variable: database in C:\inetpub\wwwroot\cmu\include\session.php on line 52
PHP Fatal error:  Call to a member function login() on a non-object in C:\inetpub\wwwroot\cmu\include\session.php on line 52

I have seen some suggestions that would suggest putting the new database object inside the Session class declaration but I want to avoid doing so because I use the database class several other places in the code and I don’t want to open up multiple connections to the database.

Answer 1

since you want to have acces on a globally set variable, you can either gain access to it with global:

function processlogin($username, $password){
    global $database;
    $database->login($username, $password);
}

or use the variable as a parameter for the contructor and remember the database object reference in the class Session:

class Session{

    private $database;

    function __construct($database){
        $this->$database = $database;
    }

    function processlogin($username, $password){
        $this->database->login($username, $password);
    }

}

and then you call:

$database = new MySQLDB();
$session = new Session($database);

this comes in handy, if you use more functions afterwords, that also need access to the database object.