FRONTEND_MVC/modules/manager/views/docs/_cat.php

<?php

use yii\helpers\Html;
use yii\widgets\ActiveForm;
use yii\web\View;

?>
<div class="cat-form">

    <?php $form = ActiveForm::begin(); ?>
  <div id="tabs-1">

    <?= $form->field($model, 'cat')->textInput(['maxlength' => true]) ?>

  </div>  

    <div class="form-group">
        <?= Html::submitButton('Save', ['class' => 'btn btn-success']) ?>
    </div>

    <?php ActiveForm::end(); ?>

</div>