【Laravel】How important it is to set "fillable" or "guarded" in model files

*Version of Laravel ...8.83.26

In Laravel, when you make model you need to add "fillable" or "guarded" to store/update records.
The columns that are set in "$fillable" are supposed to be mass assigned. "$guarded" is opposite. (These are used to block malicious request in mass assignment.)

Here is an example code for controller and model.

//BookController.php
public function store(Request $request){
  $book=Book::create($request->all());
...}

//BookModel.php
...
use Illuminate\Database\Eloquent\Model;

class Book extends Model
{
    protected $fillable=[
        'title','author'
    ];
}

In your browser, you input the title and author of the book and click "submit" button.

What happens if you forget to add "$fillable" or "$guarded"?

If you forget to add "$fillable" or "$guarded", you will get an error as below. That means, you must set either of them.

[2022-11-23 08:23:14] local.ERROR: Add [title] to fillable property to allow mass assignment on [App\Models\Book].

What happens if you have misspelling in $fillable?

If you have a misspelling...('autor' should be 'author') in "$fillable", for example,

    protected $fillable=[
        'title','autor'
    ];

you will get an error, of course.

[previous exception] [object] (PDOException(code: HY000): SQLSTATE[HY000]: General error: 1364 Field 'author' doesn't have a default value at...

What if you set "$guarded"?

On the other hand, if you set "$guarded",

    protected $guarded=[
        'title','author'
    ];

you will have an error because you tried to store(insert) data into the DB despite that data in the columns ('title','author') are not supposed to beassigned.

[2022-11-22 09:54:04] local.ERROR: SQLSTATE[HY000]: General error: 1364 Field 'title' doesn't have a default value (SQL: insert into books (updated_at, created_at) values (2022-11-22 09:59:33, 2022-11-22 09:59:33))

Tips

Those error massages always start with "Field '' doesn't have a default value." So, if you find this phrase in your error log, check your "$fillable" or "$guarded" settings in model files to make sure that you did not forget to set them, or the name of the columns are correct.