if(!class_exists('DB')) {
    class DB {
        public function __construct() {
            $mysqli = new mysqli(__HOST__, __USER__, __DB__, __PW__);
            if($mysqli->connect_errno) {
                die('%s', $mysqli->connect_error);
            }
            $this->connection =  $mysqli;
        }
        public function login($username, $password) {
			$password = strtoupper(hash('whirlpool', $password));
			$query = mysqli->query("SELECT username, password FROM users WHERE username=$Username AND password=$Password");
			if(mysqli->num_rows($this->connection, $query) == 1) {
				//cleared to go!
				$this->connection->close //always close your connections!
			} else {
				echo "Account not found or invalid credentials."
				$this->connection->close //always close your connections!
			}


        }
    }
}