When a form is based upon a model, the common way of creating this form in Yii is via the yiiwidgetsActiveForm class. In most cases, a form has a corresponding model which is used for data validation. If the model represents data from a database, then the model should be derived from the ActiveRecord class. If the model captures arbitrary input, it should be derived from the yiibaseModel class.

Let us create a registration form.

Step 1 − Inside the models folder, create a file called RegistrationForm.php with the following code.

<?php
   namespace appmodels;
   use Yii;
   use yiibaseModel;
   class RegistrationForm extends Model {
      public $username;
      public $password;
      public $email;
      public $subscriptions;
      public $photos;
      /**
      * @return array customized attribute labels
      */
      public function attributeLabels() {
         return [
            ''username'' => ''Username'',
            ''password'' => ''Password'',
            ''email'' => ''Email'',
            ''subscriptions'' => ''Subscriptions'',
            ''photos'' => ''Photos'',
         ];
      }
   }
?>

We have declared a model for our registration form with five properties − username, password, email, subscriptions, and photos.

Step 2 − To display this form, add the actionRegistration method to the SiteController.

public function actionRegistration() {
   $mRegistration = new RegistrationForm();
   return $this->render(''registration'', [''model'' => $mRegistration]);
}

We create an instance of the RegistrationForm and pass it to the registration view. Now, it is time to create a view.

Step 3 − Inside the views/site folder, add a file called registration.php with the following code.

<?php
   use yiibootstrapActiveForm;
   use yiibootstrapHtml;
?>
<div class = "row">
   <div class = "col-lg-5">
      <?php $form = ActiveForm::begin([''id'' => ''registration-form'']); ?>
      <?= $form->field($model, ''username'') ?>
      <?= $form->field($model, ''password'')->passwordInput() ?>
      <?= $form->field($model, ''email'')->input(''email'') ?>
      <?= $form->field($model, ''photos[]'')->fileInput([''multiple''=>''multiple'']) ?>
      <?= $form->field($model, ''subscriptions[]'')->checkboxList([''a'' => ''Item A'',
         ''b'' => ''Item B'', ''c'' => ''Item C'']) ?>
      <div class = "form-group">
         <?= Html::submitButton(''Submit'', [''class'' => ''btn btn-primary'',
            ''name'' => ''registration-button'']) ?>
      </div>
      <?php ActiveForm::end(); ?>
   </div>
</div>

We observe the following −

• The ActiveForm::begin() function marks the beginning of the form. All the code between ActiveForm::begin() and ActiveForm::end() functions will be wrapped within the form tag.

• To create a field in the form you should call the ActiveForm::field() method. It creates all the input and label tags. Input names are determined automatically.

• For example, the password attribute will be RegistrationForm[password]. If you want an attribute to take an array, you should append [ ] to the attribute name.

Step 4 − If you go to the address bar of the web browser and type http://localhost:8080/index.php?r=site/registration, you will see our form.