The steps to create a form using ActiveForm widget in Yii2 are as follows: 1. Create an ActiveForm instance in the view file with ActiveForm::begin() and ActiveForm::end(); 2. Add a form field using $form->field($model, 'attribute') and select appropriate input types such as textInput, passwordInput, etc.; 3. Add a submission button using Html::submitButton() and make sure that the model defines validation rules for automatic verification; 4. You can customize the form style and layout by wrapping fields, custom templates, or integrated CSS frameworks such as Bootstrap. In addition, when uploading files, you need to set enctype="multipart/form-data". For model-free forms, you can pass ordinary arrays or dynamic objects instead of the model.

Using the ActiveForm widget in Yii2 to create forms is straightforward once you understand the basic structure and methods involved. Here's how to get started, along with some practical tips for using it effectively.

Basic Setup of ActiveForm

To begin, you need to create an instance of ActiveForm inside your view file. This is usually done using a begin() and end() block.

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

<?php $form = ActiveForm::begin(); ?>

    <!-- form fields go here -->

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

This wraps your form content and handles things like opening and closing <form> tags, CSRF protection, and more.

One thing to note: always wrap your form in a variable ( $form in this case), because you'll use that variable to generate individual input fields.

Creating Input Fields

Inside the ActiveForm block, you can start adding form elements using the $form->field($model, 'attribute') method. Each field is typically associated with a model attribute.

Here's a simple example:

 <?= $form->field($model, &#39;username&#39;)->textInput([&#39;maxlength&#39; => true]) ?>

This will generate a label, an input field, and any validation error message automatically. You can customize the input type depending on what kind of data you're collecting:

• textInput() – For regular text inputs
• passwordInput() – For password fields
• dropDownList() – For dropdowns
• checkbox() – For checkboxes
• fileInput() – For file uploads (don't forget to set enctype="multipart/form-data" in the form tag)

You might also want to add hints or placeholders:

 <?= $form->field($model, &#39;email&#39;)->textInput([&#39;placeholder&#39; => &#39;you@example.com&#39;]) ?>
<?= $form->field($model, &#39;notes&#39;)->textarea([&#39;rows&#39; => 3]) ?>

If you're working with model-less forms (like search forms), you can still use ActiveForm , but you'll need to pass a plain array or dynamic object instead of a model.

Submit Button and Validation

Once all the fields are in place, you need a submit button. Use Html::submitButton() to create one:

 <?= Html::submitButton(&#39;Submit&#39;, [&#39;class&#39; => &#39;btn btn-primary&#39;]) ?>

Validation is handled automatically if your model has rules defined. For example, if your model includes:

 public function rules()
{
    Return [
        [['username', 'email'], 'required'],
        ['email', 'email'],
    ];
}

Then the form will show errors under each relevant field when validation fails.

A few tips:

• Make sure your controller properly loads and saves the model.
• Always check for $model->load(Yii::$app->request->post()) && $model->validate() before saving.
• If you're uploading files, remember to include 'enctype' => 'multipart/form-data' in the form options:

 <?php $form = ActiveForm::begin([&#39;options&#39; => [&#39;enctype&#39; => &#39;multipart/form-data&#39;]]); ?>

Styling and Layout Customization

By default, ActiveForm generates Bootstrap-compatible markup if you're using the Bootstrap asset bundle. But you can change how fields look by modifying their templates or wrapping them in custom HTML.

For example, to adjust the layout of a specific field:

 <?= $form->field($model, &#39;agree&#39;)->checkbox()->label(&#39;I agree to the terms&#39;) ?>

Or wrap fields in a grid system:

 <div class="row">
    <div class="col-md-6">
        <?= $form->field($model, &#39;first_name&#39;)->textInput() ?>
    </div>
    <div class="col-md-6">
        <?= $form->field($model, &#39;last_name&#39;)->textInput() ?>
    </div>
</div>

If you need more control, you can customize the field template globally or per-field:

 <?= $form->field($model, &#39;username&#39;, [
    &#39;template&#39; => "{label}\n<div class=\"custom-input\">{input}</div>\n{error}"
])->textInput() ?>

That's the core of working with ActiveForm . It gives you a clean way to build forms quickly while keeping validation and rendering consistent. Just make sure your models have proper rules and you're handling data correctly in your controllers.

Basically that's it.

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