extending a class

[nikko50]

Hi all!
I'm new to class files and trying to learn.
I have a database class that just establishes a connection to the db like below. How would I use the the $db objects methods within a function like below. Do I have to extend the class or can I just pass the "$db" object to the function? How would you guys do it?

//Require DB Info
require_once(DIR_WS_CLASSES . 'db.class.php');

//Create DB Object
$db = new db_class();

//Open up the database connection.

if (!$db-> connect())
$db->print_error();

function get_invoice(){

 $sql="SELECT  * FROM ".TBL_INVOICES."
       WHERE id = $_POST[rowid] ";  
 $r = $db-> select($sql);  
 $row = $db->get_row($r);

return $row;
}

[NogDog]

I would probably pass it to the function as a function parameter. If using PHP 5+, you can use type-hinting to ensure that the passed value is an object of that type:

function get_invoice(db_class $db) {
   // use $db to refer to the db_class object.
}