Laravel: immutable Trait - laravel

Question

I need that when a document is considered closed, you won't be able to modify, update or delete it anymore.
I was thinking to use a trait like an "ImmutableTrait".
I've done this:
<?php
namespace App\Traits;
use Illuminate\Database\Eloquent\Model;
trait ImmutableTrait
{
protected $isImmutable = false;
public function setAttribute($key, $value)
{
if ($this->isImmutable) {
return $this;
}
return parent::setAttribute($key, $value);
}
}
Then in my model:
use Illuminate\Database\Eloquent\Model;
use App\Traits\ImmutableTrait;
class MedicalRecord extends Model
{
use ImmutableTrait;
public function closeDocument()
{
$this->isImmutable = true;
}
}
Finally the controller:
public function closeDocument(Document $document)
{
.....
$document->closeDocument();
$document->saveorfail();
}
Then, if I try to retrieve the closed model and update a field, I shouldn't be able to do it:
Route::put('{document}/updateStatus', 'DocumentController#updateStatus');
class DocumentController extends Controller
{
....
public function updateStatus(Document $document)
{
$document->status= "TEST";
$document->saveorfail();
}
}
Calling the API with the id of a closed document, should fail the update, but this is not happening. The field is updated normally.
Obviously I'm missing something. But what?
Thank you all!

Answer 1

Just for reference if anyone needs this.
I ended up creating the following trait:
<?php
namespace App\Traits;
use App\Exceptions\ImmutableModelException;
trait ImmutableModelTrait {
public function __set($key, $value)
{
if ($this->isClosed)
{
throw new ImmutableModelException();
}
else {
//do what Laravel normally does
$this->setAttribute($key, $value);
}
}
}
The problem with my first solution, as #mrhn stated in one comment, was that I was searching for the "isImmutable" variable on a new model instance but I wasn't persisting that variable in the DB table.
So now my "Document" table has a field "isClosed" that becomes true when the document is considered closed.