Cara menampilkan auto increment otomatis pada form

<?php
include "config.php";
$sql = "SELECT * FROM filetbl ";
$result = mysqli_query($conn, $sql);
$di=1;
$tot = array();
while($row = mysqli_fetch_row($result))
{
  $tot[$di]=str_replace('','',$row[0]);
  $di++;
}
  if(count($tot)==0){
    $akhir=1;
  }else{
    $akhir = max($tot);
    $akhir++;
  }
  $id = "".$akhir;
?>

<div class="row">
  <!-- left column -->
  <div class="col-md-6">
    <!-- general form elements -->
    <div class="box box-primary">
    <div class="box-header">
      <p>Upload file Anda dengan melengkapi form di bawah ini. File yang bisa di Upload hanya file dengan ekstensi .doc, .docx, .xls, .xlsx, .ppt, .pptx, .pdf, .rar, .zip dan besar file (file size) maksimal hanya 2 MB.</p>
    </div><!-- /.box-header -->
      <!-- form start -->
      <form action="upload_tambah.php" method="post" enctype="multipart/form-data">
        <div class="box-body">
          <div class="form-group"><label>ID</label>
            <input type="text" name="id_file" class="form-control" value="<?php echo $id; ?>">
          </div>
          <div class="form-group"><label>Email</label>
            <input type="text" name="email" class="form-control" placeholder="Isikan email tujuan" required>
          </div>
          <div class="form-group"><label>Komentar</label>
            <textarea name="isi" class="form-control" placeholder="Isikan komentar Anda"></textarea>
          </div>
          <div class="form-group"><label>Pilih File</label>
            <input type="file" name="data_upload" required>
          </div>
        </div><!-- /.box-body -->
        <div class="box-footer">
          <button type="submit" name="submit" class="btn btn-primary">Submit</button>
        </div>
      </form>
    </div><!-- /.box -->
  </div><!--/.col (left) -->
</div>   <!-- /.row -->