backend/views/settings/_codes_tab.php

<?php
    use common\models\Settings;
    use yii\bootstrap\ActiveForm;
    use yii\web\View;
    
    /**
     * @var View       $this
     * @var Settings   $model
     * @var ActiveForm $form
     */
    echo $form->field($model, 'analytics_key')
              ->textInput();