**Course Title:** Mastering Yii Framework: Building Scalable Web Applications **Section Title:** Form Handling and Validation **Topic:** Build a form for user input, implement validation, and handle errors in a Yii application.(Lab topic) **Objective:** By the end of this topic, you will be able to create a form for user input, implement validation rules, and handle errors in a Yii application. You will learn how to use Yii's built-in form handling and validation features to ensure that user input is valid and secure. **Prerequisites:** * You have completed the previous topics in the course, including "Introduction to Yii and Development Environment," "Routing, Controllers, and Views," and "Database Management with Active Record." * You have a basic understanding of HTML, CSS, and PHP. **Step 1: Create a Form for User Input** To create a form for user input, you will need to create a new view file in the `views` directory of your Yii application. In this example, we will create a form for user registration. Create a new file called `register.php` in the `views/site` directory: ```php // views/site/register.php use yii\helpers\Html; ?> <?= Html::beginForm('/site/register', 'post') ?> <?= Html::label('Username:', 'username') ?> <?= Html::textInput('username', '', ['class' => 'form-control']) ?> <?= Html::label('Email:', 'email') ?> <?= Html::emailInput('email', '', ['class' => 'form-control']) ?> <?= Html::label('Password:', 'password') ?> <?= Html::passwordInput('password', '', ['class' => 'form-control']) ?> <?= Html::submitButton('Register', ['class' => 'btn btn-primary']) ?> <?= Html::endForm() ?> ``` This code creates a simple form with three input fields: username, email, and password. **Step 2: Implement Validation Rules** To implement validation rules, you will need to create a new model file in the `models` directory of your Yii application. In this example, we will create a model for user registration. Create a new file called `User.php` in the `models` directory: ```php // models/User.php namespace app\models; use yii\db\ActiveRecord; class User extends ActiveRecord { public static function tableName() { return 'users'; } public function rules() { return [ [['username', 'email', 'password'], 'required'], [['username', 'email'], 'string', 'max' => 255], [['password'], 'string', 'min' => 6], [['email'], 'email'], [['username'], 'unique'], ]; } } ``` This code defines a model for user registration with four validation rules: * `username` and `email` are required and must be strings with a maximum length of 255 characters. * `password` is required and must be a string with a minimum length of 6 characters. * `email` must be a valid email address. * `username` must be unique. **Step 3: Handle Errors** To handle errors, you will need to create a new controller file in the `controllers` directory of your Yii application. In this example, we will create a controller for user registration. Create a new file called `SiteController.php` in the `controllers` directory: ```php // controllers/SiteController.php namespace app\controllers; use yii\web\Controller; use app\models\User; class SiteController extends Controller { public function actionRegister() { $model = new User(); if ($model->load(Yii::$app->request->post()) && $model->save()) { return $this->redirect(['site/index']); } else { return $this->render('register', ['model' => $model]); } } } ``` This code defines a controller for user registration that loads the user model, checks if the form is valid, and saves the user data if the form is valid. **Conclusion:** In this topic, you learned how to create a form for user input, implement validation rules, and handle errors in a Yii application. You can use this knowledge to create secure and scalable web applications. **Exercise:** Create a form for user login and implement validation rules to ensure that the user input is valid. **Additional Resources:** * Yii Framework Documentation: <https://www.yiiframework.com/doc/> * Yii Framework Tutorials: <https://www.yiiframework.com/tutorials/> * Yii Framework Forum: <https://www.yiiframework.com/forum/> **Leave a comment or ask for help:** If you have any questions or need help with this topic, please leave a comment below.