title: yii2 not saving all fields
body: <p>I have this User model:</p>
  
  <pre><code>  public $id;
      public $username;
      public $name;
      public $password;
      public $authKey;
      public $accessToken;
  </code></pre>
  
  <p>and this Form model </p>
  
  <pre><code>  class SignupForm extends Model
  
  {
      public $username;
      public $name;
      public $email;
      public $password;
      public $fio;
      public $phone;
  </code></pre>
  
  <p>And I try to save:</p>
  
  <pre><code>$user = new User();
              $user-&gt;username = $this-&gt;username;
              $user-&gt;name = $this-&gt;name;
              $user-&gt;email = $this-&gt;email;
              var_dump($this-&gt;username);
              var_dump($user-&gt;username);
              var_dump($this-&gt;name);
              var_dump($user-&gt;name);
  
              $user-&gt;save(false);
  </code></pre>
  
  <p>But in the database table this only saves the email field. All data in <code>var_dump</code> are correct.</p>