Baixe o csv do codeigniter mysql

$this->load->model('Users_model');
$this->Users_model->csv();

function csv()
{
        $this->load->dbutil();
        $this->load->helper('file');
        $this->load->helper('download');
        $query = $this->db->query("SELECT * FROM Users");
        $delimiter = ",";
        $newline = "\r\n";
        $data = $this->dbutil->csv_from_result($query, $delimiter, $newline);
        force_download('CSV_Report.csv', $data);
}