Field 'user_id' is empty - php

Question

Today I have made a comments system, but isn't completed.In my database I have all fields filled by dates, but user_id isn't.How can I be able to save in column user_id, the id of authenticated user?Here is my code.
CommentsController:
public function store(Request $request, $post_id)
{
$this->validate($request, array(
'username' => 'required|max:255',
'mail' => 'required|mail|max:255',
'comment' => 'required|min:5|max:2000',
));
$post = Post::find($post_id);
$comment = new Comment();
$comment->username = $request->username;
$comment->email = $request->email;
$comment->comment = $request->comment;
$comment->approved = true;
$comment->post()->associate($post);
$comment->save();
Session::flash('message', "Message posted successfully!");
return Redirect::back();
}
My view
<div class="row">
<div id="comment-form">
{{ Form::open(['route' => ['comments.store', $post->id], 'method' => 'POST']) }}
<div class="row">
<div class="col-md-6">
{{ Form::label('username', "Username:") }}
{{ Form::text('username', null, ['class' => 'form-control']) }}
</div>
<div class="col-md-6">
{{ Form::label('email', "Email:") }}
{{ Form::text('email', null, ['class' => 'form-control']) }}
</div>
<div class="col-md-6">
{{ Form::label('comment', "Comment:") }}
{{ Form::text('comment', null, ['class' => 'form-control']) }}
</div>
{{ Form::submit('Add Comment', ['class' => 'btn btn-success btn-xs']) }}
</div>
{{ Form::close() }}
</div>
My route
Route::post('comments/{post_id}', ['uses' => 'CommentsController#store', 'as' => 'comments.store']);
I tried to put Auth::user()->id inside my form, but I failed...

Answer 1

For you get the authenticated user you should only use the Auth facade. I show how to use it below.
use Illuminate\Support\Facades\Auth;
$user = Auth::user(); // Get the currently authenticated user...
$user_id = Auth::id(); // Get the currently authenticated user's ID...
Therefore, to save a user associated in a comment you have two options:
$user_id = Auth::id();
$comment->user_id = $user;
$comment->save();
Or
$user = Auth::user();
$comment->user = $user;
$comment->save();
If you have more questions about Laravel authentication take a look at https://laravel.com/docs/5.8/authentication#retrieving-the-authenticated-user.