HTTP ERROR 500 when running to linux server?

I have this PHP code for importing excel to mysql using PhpSpreadsheet in xampp. This code is OK when running in windows environment but if I hosted it to a Linux Server(Ubuntu 22.04) using XAMPP Linux got an error "HTTP ERROR 500". I've installed all packages and extension needed for PhpSpreadsheet based here on phpspreadsheet.readthedocs.io documentation. If this error is for the server side what should I do? Please help

These are my codes for my import file

composer.json

{
"name": "mark/import1",
"autoload": {
    "psr-4": {
        "Mark\\Import1\\": "src/"
    }
},
"authors": [
    {
        "name": "mark"
    }
],

 "require": {
    "phpoffice/phpspreadsheet": "^1.28"
},
"config": {
    "platform": {
        "php": "8.1"
    }
}
}

import code

<?php
 $con = mysqli_connect('localhost','root','','db_import');

 require 'vendor/autoload.php';

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

  if(isset($_POST['save_excel_data']))
  {
   $fileName = $_FILES['import_file']['name'];
   $file_ext = pathinfo($fileName, PATHINFO_EXTENSION);

   $allowed_ext = ['xls','csv','xlsx'];

  if(in_array($file_ext, $allowed_ext))
  {
    $inputFileNamePath = $_FILES['import_file']['tmp_name'];
    $spreadsheet = \PhpOffice\PhpSpreadsheet\IOFactory::load($inputFileNamePath);
    $data = $spreadsheet->getActiveSheet()->toArray();

foreach($data as $row)
{
            $fullname = $row['0'];
            $email = $row['1'];
            $phone = $row['2'];
            $course = $row['3'];
    
    $studentQuery = "INSERT INTO students (fullname,email,phone,course) 
                            VALUES('$fullname','$email','$phone','$course')";
            $result = mysqli_query($con, $studentQuery);
            $msg = true;    
}
 }
 }