Подскажите пожалуйста, как правильно вызвать метод из другого класса?

Есть кот

class core {
	function __construct() {
		$this->db_server   = 'phpforum.ru';
		$this->db_username = 'phpforum';
		$this->db_password = '';
		$this->db_name     = 'phpforum_db';
	}
	
	function db_core_connect() {
		$this->link = mysql_connect($this->db_server, $this->db_username, $this->db_password);
		mysql_select_db($this->db_name, $this->link);
		$this->sql = "set names utf8";
		mysql_query($this->sql, $this->link);
		return $this->link;
	}
}

class user {
	function login() {
		$this->link = core::db_core_connect(); // Здесь что-то не так :)
	}
	
}

Warning: mysql_connect() [function.mysql-connect]: Access denied for user 'user'@'localhost' (using password: NO) in Z:\home\...\classes.php on line 32

Warning: mysql_select_db() expects parameter 2 to be resource, boolean given in Z:\home\...\classes.php on line 33

Warning: mysql_query() expects parameter 2 to be resource, boolean given in Z:\home\...\classes.php on line 35