public function connect($host, $ssl = false, $port = 21, $timeout = 90)
    {
        if ($ssl) {
            $this->connection = @ftp_ssl_connect($host, $port, $timeout);
        } else {
            $this->connection = @ftp_connect($host, $port, $timeout);
        }

        if ($this->connection == null) {
            throw new Exception('Unable to connect');            
        } else {
            return $this;
        }
    }