the class:

class User {

	var $userID,
		 $userName,
		 $userPassword,
		 $host,
		 $dbUser,
		 $dbPassword,
		 $dbTable,
		 $dbName;

	function User(){

		$this->dbUser = 'OOP';
		$this->dbPassword = 'xxxxx';
		$this->dbName = 'OOP';
		$this->dbTable = 'usersExample';
		$this->host = 'localhost';

	}

		function registerUser($userName, $userPassword){
			$link = mysql_connect($this->host, $this->dbUser, $this->$dbPassword);
			if(!$link){
				die('Could not connect: ' . mysql_error());
			}
			else {
				echo 'Connected';
			}
			mysql_close($link);
		}

test.php

include('class_user.php');

$test = new User;

$user = 'Craig';
$pass = 'yoyo';

$test->registerUser($user, $pass);