test1/public/basic/models/UpdateForm.php

<?php

namespace app\models;

use Yii;
use yii\base\Model;
use app\models\TestUsers;

class UpdateForm extends Model
{
    public $username;
    public $accessToken;
    public $authKey;
    public $password;
    public $forename;
    public $surname;
    public $email;
    public $phone;
    public $lang;

    public function rules(){
        return [
            ['email', 'trim'],
            ['email', 'string', 'min' => 2, 'max' => 255],
            ['phone', 'trim'],
            ['phone', 'string', 'min' => 2, 'max' => 32],
            ['lang', 'string', 'min' => 2, 'max' => 10],
        ];
    }

    public function update(){
        if ($this->validate()){
            $user = TestUsers::findOne(Yii::$app->user->id);
            if ($this->email !== '') {
                $user->email = $this->email;
            }
            if ($this->phone !== '') {
                $user->phone = $this->phone;
            }
            $user->lang = $this->lang;
            Yii::$app->language = $this->lang;
            $user->save();
            return true;
        }
        return false;
    }

}