如何在yii2中构建多个模型的形式？

I am trying to create a form that use multiple model instances and submit them all at once (tabular input), i have read this article on wiki yiiframework , but what i am trying to do is to build a custom model that contains properties and attributes from multiple models then use this model in my form.

[Example]

model1

namespace app\models;

use Yii;
use \yii\db\ActiveRecord;

class Country extends ActiveRecord
{
   ........
}

molel2

 namespace app\models;

use Yii;
use \yii\db\ActiveRecord;

class User extends ActiveRecord
{
   ........
}

Creating your own model is simple. The more detailed explanation could be found by following link.

Your own model might look like this:

namespace app\models;

use yii\base\Model;

class Custom extends Model
{
    public $name;
    public $surname;
    public $email;
    public $country;
    public $city;

    public function rules()
    {
        return [
        // the name, surname, city attributes are required
        [['name', 'surname', 'country', 'city'], 'required'],

        // the email attribute should be a valid email address
        ['email', 'email'],
    ];
    }

    public function customFunction()
    {
        //some custom things
    }
}