datatable.directory/app/Tables/CsvExporter.php

<?php


namespace App\Tables;


class CsvExporter extends BaseExporter
{
    /**
     * @return string - mime type for the downloaded file
     */
    protected function getMimeType()
    {
        return $this->wantDownload ? 'text/csv' : 'text/plain';
    }

    /**
     * @return string - file extension for the downloaded file
     */
    protected function getFileExtension()
    {
        return 'csv';
    }

    /**
     * Write the document to stdout ('php://output')
     */
    protected function writeDocument()
    {
        $handle = fopen('php://output', 'w');

        $columnNames = array_map(function (Column $c) {
            return $c->title;
        }, $this->columns);

        fputcsv($handle, $columnNames);

        foreach ($this->iterateRows() as $row) {
            $items = [];
            foreach ($this->columns as $column) {
                if (isset($row->{$column->name})) {
                    $items[] = $row->{$column->name};
                } else {
                    $items[] = null;
                }
            }
            fputcsv($handle, $items);
        }

        fclose($handle);
    }
}