php - Yii 2.0 - Input values saved as null in database -

in practice app, have table called 'music' 3 columns - id, title , artist. whenever try insert input values form database, new record added id has value, title , artist both null. below model:

<?php namespace app\models;  /** * model class table "music". * * @property integer $id * @property string $title * @property string $artist */ class musicentry extends \yii\db\activerecord { public $title; public $artist; public $id;  public static function tablename() {     return 'music'; }  public function rules() {     return [             [['title', 'artist'], 'required'],             [['id'], 'safe'],     ]; } } ?> 

while controller action looks so:

public function actionmusicentry() {     $model = new musicentry ();      if (isset ( $_post ['musicentry'] )) {         $model->load($_post);         if ($model->save()) {             yii::$app->session->setflash ( 'success', 'model has been saved' );             $this->redirect ( [                      'music-entry',                     'id' => $model->id             ] );         }      }      return $this->render ( 'music-entry', [              'model' => $model      ] ); } 

i've tried getting value of artist , title after loading model using $_post , has values inputted in form. given this, why input values saved null in database?

after further tweaking, found cause of problem in model. had remove declaration $artist , $title. i'm still not sure though why adding variables caused such problem. still looking it.