Ok i've just started to use PHP5, got a database class set up to handle all my database querys etc.

Do I need to declare a new instance of the database class on every page?

PHP Code:
require_once('database.php');

$a = new DB();
$a->connect(); 
Its just i have a class to handle the database and a class to handle my current logged in user. Which I will need to refresh on every page (SO reload and get all the info) Is this correct way of doing it?