Using PHPSpreadsheet to create XLS files, Not Working within confines of Wordpress

Question

I need to use PHPSspreadsheet to export an excel file from a Wordpress site.

I have the package installed, and I put their test case into a function, but it isn't doing anything. I have these functions in a custom plugin file. When I put the "use PhpOffice" part into my original function it gve an error, so I understand it has to be outside of the function, but I am still not sure it is in the right spot.

I put the PHPSpreadsheet example into another function so it would run at init, but I am just hacking away here....

<?php
        use PhpOffice\PhpSpreadsheet\Spreadsheet;
        use PhpOffice\PhpSpreadsheet\Writer\Xlsx;


    //I added this function (spreadfunction) to try to have PHPSpreadsheet run at init for header reasons.

        add_action('init', 'spreadfunction');

        function spreadfunction() {


          $spreadsheet = new Spreadsheet();
          $sheet = $spreadsheet->getActiveSheet();
          $sheet->setCellValue('A1', 'Hello World !');

          $writer = new Xlsx($spreadsheet);
          $writer->save('hello world.xlsx');

        }


    //Originally, I had the sample code in this function, but no luck there, but I am using this to trigger it and so I can pass data to it ultimately.

        function update_attendance_report_function() {

        spreadfunction();
        exit;

        }

        add_action( 'admin_post_nopriv_attendance_report', 'update_attendance_report_function' );
        add_action( 'admin_post_attendance_report', 'update_attendance_report_function' );

Answer 1

try this code below...

<?php

    use PhpOffice\PhpSpreadsheet\Spreadsheet;
    use PhpOffice\PhpSpreadsheet\Writer\Xlsx;

    if (isset($_POST['export_excel'])) {

    ob_clean(); //this point <========================================

    $spreadsheet = new Spreadsheet();
    $active_sheet = $spreadsheet->getActiveSheet();
    $sheet->setCellValue('A1', 'Hello World !');

    header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
    header('Content-Disposition: attachment;filename="myfile.xlsx"');
    header('Cache-Control: max-age=0');

    $writer = \PhpOffice\PhpSpreadsheet\IOFactory::createWriter($spreadsheet, 'Xlsx');
    $writer->save('php://output');

    ob_flush(); //and this point <==========================================

} ?>