too long

I have been having issues with my user signup code of my API I am working on.

I have a UserController that takes the posted data and validates the fields. Then it will send the data to the SignUpUser method in my UserService class that makes a user model and fill in all the given data and send it to the UserRepository that sends it to my DB.

When I dd() my $password it's filled but when I dd() my filled in $user the field return null... I have no idea why it has not filled it in yet.

Screenshots of my code:

UserController

public function signUpUser(Request $request)
{
    $this->validate($request,[
        'username' => 'required|regex:/^[(a-zA-Z\s)(0-9\s)]+$/u|min:3',
        'email' => 'required|email',
        'password' => 'required|min:8',
        'displayname' => 'required|regex:/^[(a-zA-Z\s)(0-9\s)]+$/u|min:3',
    ], [
        'min' => 'The :attribute must at least be :min characters long.',
    ]);

    $user = $this->userService->signUpUser(
        $request->get('username'),
        $request->get('email'),
        $request->get('password'),
        $request->get('displayname')
    );



    if($user)
    {
        //alright! user has been made
        $response = ['status' => 'OK', 'message' => "User {$user->username} has successfully been created"];
    }
    else
    {
        //something went wrong
        $response = ['status' => 'FAIL', 'message' => "Something went wrong or user already exists in DB"];
    }

    return response()->json($response, 201);
}

UserService

public function signUpUser($userName, $email, $password, $displayName)
{
    $password = password_hash($password, PASSWORD_DEFAULT);

    $user = $this->userRepository->signUpNewUser($userName, strtolower($email), $password, $displayName);
    $user = $this->userRepository->get($user->pk);
    //TODO: send user signup mail soon
    return $user;
}

UserRepository

public function signUpNewUser($username, $email, $password, $displayName)
{
    $user = $this->getModel();
    $user->fill(
        [
            'username' => $username,
            'email' => $email,
            'password' => $password,
            'displayname' => $displayName,
        ]);
    dd($user::all());
    $user->save();
    return $user;
}

UserModel

class UserModel extends BaseModel
{

/**
 * The database table used by the model.
 *
 * @var string
 */
protected $table = 'users';


/**
 * The attributes that are mass assignable.
 *
 * @var array
 */
protected $fillable = [
'username', 'email', 'displayname'
];

/**
 * The attributes excluded from the model's JSON form.
 *
 * @var array
 */
protected $hidden = [
    'password',
];
}

Dumped $user after filling in data

Add it to $fillable:

protected $fillable = ['username', 'email', 'displayname', 'password'];

Also, do not keep unencrypted password in the DB, use bcrypt():

'password' => bcrypt($password),