数据未写入CSV文件

Question

我正在尝试将数据库表中的字段写入csv文件，但在下载之前没有任何内容写入该文件。我在网上搜索了任何可能有用的答案，但我找不到任何答案。我想要做的是使用PHP的SPLFileObject将数据从数据库表写入csv文件，但就像我说的那样，它不会将表中的数据写入文件。任何可以解决这个问题的帮助都将不胜感激。

这是我的代码：

 public function indexAction()
 {
    header('Content-Type: text/csv');
    header('Content-Disposition: attachment; filename=reports.csv');
    header('Pragma: no-cache');
    header("Expires: 0");

    $this->getExportService()->exportToCSVFile();

    exit;
 }



 /**
     * Setter method
     * @return ExportModel
     */
    public function set()
    {
        $this->spl_file = new SplFileObject(self::CSV_FILENAME, "w");

        return $this;
    }

    /**
     * Getter method
     * @return SplFileObject|null
     */
    public function get()
    {
        return $this->spl_file;
    }

     public function exportToCSVFile()
     {
       // get the fields from the order_records table

       $rows = $this->table->select();


       foreach ($rows as $fields) {
           $this->get()->fputcsv(array('id' => $fields->id, 'date' => $fields->date, 'status' => $fields->status,
               'payment_status' => $fields->payment_status, 'campaign_id' => $fields->campaign_id, 'tax' => $fields->tax,
               'shipping' => $fields->shipping, 'payment_method' => $fields->payment_method, 'buyer_email' => $fields->buyer_email,
               'paypal_payment_id' => $fields->paypal_payment_id, 'paypal_payer_id' => $fields->paypal_payer_id, 
               'buyer_name' => $fields->buyer_name, 'paypal_capture_id' => $fields->paypal_capture_id,
               'paypal_authorization_id' => $fields->paypal_authorization_id
           ));
       }
    }