upload File Code

<div class="container">
  <div class="row">
    <div class="card">
      <h3 class="headingDocument">Upload Your Document Here </h3>
    <form id="file_upload" method="post" action="#" enctype="multipart/form-data">
      <div class="form-group">
         <input type="file" name="my_file_upload[]" multiple="multiple" class="form-control">
       </div>
         <div class="form-group">

         <input name="my_file_upload" type="submit" value="Upload Now" class="btn btn-primary" />
       </div>
    </form>
  </div>
  <hr>
<?php
 $current_user_id = get_current_user_id();
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    require_once( ABSPATH . 'wp-admin/includes/image.php' );
    require_once( ABSPATH . 'wp-admin/includes/file.php' );
    require_once( ABSPATH . 'wp-admin/includes/media.php' );


    $files = $_FILES["my_file_upload"];
    foreach ($files['name'] as $key => $value) {
        if ($files['name'][$key]) {
            $file = array(
                'name' => $files['name'][$key],
                'type' => $files['type'][$key],
                'tmp_name' => $files['tmp_name'][$key],
                'error' => $files['error'][$key],
                'size' => $files['size'][$key]
            );
            $_FILES = array("upload_file" => $file);
            $attachment_id = media_handle_upload("upload_file", 0);

            if (is_wp_error($attachment_id)) {
                // There was an error uploading the image.
                echo "Error adding file";
            } else {
                // The image was uploaded successfully!
                echo "File added successfully with ID: " . $attachment_id . "<br>";
                wp_get_attachment_image($attachment_id, array(800, 600)) . "<br>"; //Display the uploaded image with a size you wish. In this case it is 800x600


            }
        }
    }
}
?>