I got it work but with table structure: title, description, keyword 
Its possible to get same working with table structure key x value?
Page preview is in first post.
model:
<?php
namespace backend\modules\setting\modules\seo\models;
use Yii;
use yii\db\ActiveRecord;
class Seo extends ActiveRecord
{
public $controllerNamespace = 'backend\modules\setting\modules\seo\controllers';
public static function tableName()
{
return '{{%seo}}';
}
public function rules()
{
return [
[['title', 'description', 'keyword'], 'trim'],
[['title'], 'required', 'message' => Yii::t('backend', 'The title field is required.')],
[['title'], 'string', 'max' => 64, 'message' => Yii::t('backend', 'The title field can not be longer than 64 characters.')],
[['description'], 'string', 'max' => 256, 'message' => Yii::t('backend', 'The description field can not be longer than 256 characters.')],
[['description'], 'string', 'max' => 256, 'message' => Yii::t('backend', 'The keywords field can not be longer than 64 characters.')],
];
}
public function attributeLabels()
{
return [
'title' => Yii::t('backend', 'Title'),
'description' => Yii::t('backend', 'Description'),
'keyword' => Yii::t('backend', 'Keywords'),
];
}
}
controller:
<?php
namespace backend\modules\setting\modules\seo\controllers;
use Yii;
use yii\web\Controller;
use yii\data\ActiveDataProvider;
use yii\filters\VerbFilter;
use yii\filters\AccessControl;
use backend\modules\setting\modules\seo\models\Seo;
class SeoController extends Controller
{
public function behaviors()
{
return [
'access' => [
'class' => AccessControl::className(),
'rules' => [
[
'allow' => true,
'roles' => ['@'],
],
],
],
];
}
public function actionIndex()
{
$model = Seo::findOne(0);
if ($model->load(Yii::$app->request->post()))
{
if ($model->validate())
{
if ($model->save(false))
{
Yii::$app->getSession()->setFlash('success', [
'type' => 'success',
'icon' => 'glyphicon glyphicon-ok-sign',
'message' => Yii::t('backend', 'SEO settings have been saved.'),
'title' => Yii::t('common', 'Success!'),
]);
return $this->redirect(['/settings/seo']);
} else
{
Yii::$app->getSession()->setFlash('error', [
'type' => 'danger',
'icon' => 'glyphicon glyphicon-remove-sign',
'message' => Yii::t('backend', 'SEO settings could not be saved.'),
'title' => Yii::t('common', 'Error!'),
]);
return $this->refresh();
}
}
}
return $this->render('index', [
'model' => $model,
]);
}
}
view:
<?php
use yii\helpers\Html;
use yii\widgets\ActiveForm;
?>
<div class="default-index seo">
<?php $form = ActiveForm::begin(['id' => 'form-seo']); ?>
<?= $form->field($model, 'title')->textInput() ?>
<?= $form->field($model, 'description')->textInput() ?>
<?= $form->field($model, 'keyword')->textInput() ?>
<div class="form-group">
<?= Html::submitButton(Yii::t('common', 'Update'), ['class' => 'btn btn-success']) ?>
</div>
<?php ActiveForm::end(); ?>
</div>
