JSON Data is not generated in excel sheet

Question

I created an bearer token generating api that creates a bearer token when a user loged in. and I also have an protected.php file that authenticate the token and create the excel sheet that contain the json data using phpspreadsheet. but in my case everything is fine but excel sheet is also generated but it doesn't contain the json data.

here is the <!--protected.php--> file

<?php
include_once './config/database.php';
require "../vendor/autoload.php";

use \Firebase\JWT\JWT;
use Firebase\JWT\Key;

// Import PHPExcel classes
use PhpOffice\PhpSpreadsheet\Spreadsheet;
use PhpOffice\PhpSpreadsheet\Writer\Xlsx;


header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");
header("Access-Control-Allow-Methods: POST");
header("Access-Control-Max-Age: 3600");
header("Access-Control-Allow-Headers: Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With");

$secret_key = "bGS6lzFqvvSQ8ALbOxatm7/Vk7mLQyzqaS34Q4oR1ew=";
$jwt = null;
$databaseService = new DatabaseService();
$conn = $databaseService->getConnection();

$data = json_decode(file_get_contents("php://input"), true);
// var_dump($data);
// die();
$authHeader = $_SERVER['HTTP_AUTHORIZATION'];

$arr = explode(" ", $authHeader);
// print_r($arr);
// die();`your text
$jwt = $arr[1];

if ($jwt) {
    try {
        // $decoded = JWT::decode($jwt, $secret_key, array('HS256'));
        $decoded = JWT::decode($jwt, new Key($secret_key, 'HS256'));
        // var_dump('$secret_key');
        // Access is granted. Add code of the operation here 
        // Convert JSON data to an array
        // $student_data = json_decode(file_get_contents("php://input"), true);
        // print_r('$data');
        // die();
        // Create a new Spreadsheet object
        $spreadsheet = new Spreadsheet();

        // Get the active worksheet
        $worksheet = $spreadsheet->getActiveSheet();

        // Set the column headers
        $worksheet->setCellValue('A1', 'Student Name');
        $worksheet->setCellValue('B1', 'Subject');
        $worksheet->setCellValue('C1', 'Obtained Marks');
        $worksheet->setCellValue('D1', 'Total Marks');

        // Set the data rows
        $row = 2;
        foreach ($data as $student) {
            $worksheet->setCellValue('A' . $row, $student['name']);
            $worksheet->setCellValue('B' . $row, $student['subject']);
            $worksheet->setCellValue('C' . $row, $student['obtained_marks']);
            $worksheet->setCellValue('D' . $row, $student['total_marks']);
            var_dump($worksheet->getCell('A' . $row)->getValue());
            var_dump($worksheet->getCell('B' . $row)->getValue());
            var_dump($worksheet->getCell('C' . $row)->getValue());
            var_dump($worksheet->getCell('D' . $row)->getValue());
            $row++;
        }

        // Create a new Excel file in the server
        // $writer = new Xlsx($spreadsheet);
        // $filename = '/home/harshraghuwanshi/www/phpproject/php-jwt-api/api/API/excel/students_data.xlsx';
        $writer = \PhpOffice\PhpSpreadsheet\IOFactory::createWriter($spreadsheet, 'Xlsx');
        $writer->save('/home/harshraghuwanshi/www/phpproject/php-jwt-api/api/API/excel/students.xlsx');

        // $writer->save($filename);

        // Download the file to the client
        header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
        header('Content-Disposition: attachment;filename="' . $filename . '"');
        header('Cache-Control: max-age=0');
        $writer->save('php://output');
        // readfile($filename);

        echo json_encode(array(
            "message" => "Access granted"
        ));
    } catch (Exception $e) {
        http_response_code(401);
        // print_r($e->getTrace());
        // die();
        echo json_encode(array(
            "message" => "Access denied",
            "error" => $e->getMessage()
        ));
    }
} else {
    http_response_code(401);

    echo json_encode(array(
        "message" => "Access denied: token not provided"
    ));
}

I try to solve the problem in several ways I debug $data variable do var_dump on different lines but still i don't get the problem.

please help me.