Cara memberikan Password Portal Kampus saat download file

Assalam,.. sepertinya perlu tambahan filed password did atabase, jadi saat upload file di admin input password dulu,
jadi saat download nanti perlu mengecek di controllersnya,..
$cek_pass = $this->db->query("SELECT * FROM download where nama_file='$_GET[file]' AND password!=''");
if ($cek_pass->num_rows()>=1){
echo "<form action='' method='POST'>
              <input type='hidden' name='file' value='$_GET[file]'>
              <input type='password' name='password'>
              <input type='submit' name='submit' value='Download'>
           </form>";
}else{
   // Langsung akses download
  $name = $_POST[file];
  $data = file_get_contents("asset/files/".$name);
  force_download($name, $data);
}
 
if (isset($_POST['submit'])){
$cek_valid = $this->db->query("SELECT * FROM download where nama_file='$_POST[file]' AND password='$_POST[password]'");
if ($cek_valid ->num_rows()>=1){
   // Langsung akses download,...
  $name = $_POST[file];
  $data = file_get_contents("asset/files/".$name);
  force_download($name, $data);
}else{
  // Munculkan Pemberitahuan Password salah....
}

maaf pak sya tidak terlalu mengerti soal penempatan kodenya, bisa di jelaskan proses awalnya atau langkah-langkahnya pak.
terima kasih, maaf kwl merepotkan.

Assalam,.. 
ini error nya dimana yah gan,,,,selalu error saat input db,,,mohon solusinya gan....