Mysql不接受表单输入Laravel 5.2

Newbie to PHP and Laravel 5.2. I created a users table with php artisan make:auth, but want to add two more columns to my database. I was able to add the columns in the database, but when I register new users it accepts everything but first_name and last_name in mysql which come up blank. I don't understand what I'm missing?

    Schema::create('users', function (Blueprint $table) {
        $table->increments('id');
        $table->string('first_name');
        $table->string('last_name');
        $table->string('email')->unique();
        $table->string('avatar')->default('default.jpg');
        $table->string('password');
        $table->rememberToken();
        $table->timestamps();
        });

My AuthController file

   protected function validator(array $data)
{
    return Validator::make($data, [
        'first_name' => 'required|max:255',
        'last_name' => 'required|max:255',
        'email' => 'required|email|max:255|unique:users',
        'password' => 'required|min:6|confirmed',
    ]);
}


protected function create(array $data)
{
    return User::create([
        'first_name' => $data['first_name'],
        'last_name' => $data['last_name'],
        'email' => $data['email'],
        'password' => bcrypt($data['password']),
    ]);

Example of form input for first_name on register.blade

<div class="form-group{{ $errors->has('first_name') ? ' has-error' : '' }}">
                        <label class="col-md-4 control-label">First Name</label>

                        <div class="col-md-6">
                            <input type="text" class="form-control" name="first_name" value="{{ old('first_name') }}">

                            @if ($errors->has('first_name'))
                                <span class="help-block">
                                    <strong>{{ $errors->first('first_name') }}</strong>
                                </span>
                            @endif
                        </div>
                    </div>

As @Sid stated, these fields need to be mass-assignable, which is described in the docs:

You may also use the create method to save a new model in a single line. [...] before doing so, you will need to specify either a fillable or guarded attribute on the model, as all Eloquent models protect against mass-assignment.

From https://laravel.com/docs/5.2/eloquent#mass-assignment

class Flight extends Model
{
    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = ['name'];
}