guide WIP [skip ci]

docs/guide/start-forms.md

@@ -5,14 +5,14 @@ Working with Forms
 
 In this section, we will describe how to create a new page to get data from users.
 The page will display a form with a name input field and an email input field.
-After getting the data entered by a user, the page will echo them back to the user for confirmation.
+After getting these data from a user, the page will echo them back to the user for confirmation.
 
 To achieve this goal, besides creating an [action](structure-controllers.md) and
 two [views](structure-views.md), you will also create a [model](structure-models.md).
 
 Through this tutorial, you will learn
 
-* How to create a [model](structure-models.md) to represent the data entered by users;
+* How to create a [model](structure-models.md) to represent the data entered by a user;
 * How to declare rules to validate the data entered by users;
 * How to build an HTML form in a [view](structure-views.md).
 
@@ -20,9 +20,96 @@ Through this tutorial, you will learn
 Creating a Model
 ----------------
 
+To represent the data entered by a user, create an `EntryForm` model class as shown below and
+save the class in the file `models/EntryForm.php`. Please refer to the [Class Autoloading](concept-autoloading.md)
+section for more details about the class file naming convention.
+
+```php
+namespace app\models;
+
+use yii\base\Model;
+
+class EntryForm extends Model
+{
+    public $name;
+    public $email;
+
+    public function rules()
+    {
+        return [
+            [['name', 'email'], 'required'],
+            ['email', 'email'],
+        ];
+    }
+}
+```
+
+The class extends from [[yii\base\Model]], a base class provided by Yii that is commonly used to
+represent form data.
+
+The class contains two public members, `name` and `email`, which are used to keep
+the data entered by the user. It also contains a method named `rules()` which returns a set
+of rules used for validating the data. The validation rules declared above state that
+
+* both the `name` and `email` data are required;
+* the `email` data must be a valid email address.
+
+If you have an `EntryForm` object populated with the data entered by a user, you may call
+its [[yii\base\Model::validate()|validate()]] to trigger the data validation. A data validation
+failure will turn on the [[yii\base\Model::hasErrors|hasErrors]] property, and through
+[[yii\base\Model::getErrors|errors]] you may learn what validation errors the model has.
+
+
 Creating an Action
 ------------------
 
+Next, create an `entry` action in the `site` controller, like you did in the previous section.
+
+```php
+namespace app\controllers;
+
+use Yii;
+use yii\web\Controller;
+use app\models\EntryForm;
+
+class SiteController extends Controller
+{
+    // ...existing code...
+
+    public function actionEntry()
+    {
+        $model = new EntryForm;
+
+        if ($model->load(Yii::$app->request->post()) && $model->validate()) {
+            // valid data received in $model
+
+            // do something meaningful here about $model ...
+
+            return $this->render('entry-confirm', ['model' => $model]);
+        } else {
+            // either the page is initially displayed or there is some validation error
+            return $this->render('entry', ['model' => $model]);
+        }
+    }
+}
+```
+
+The action first creates an `EntryForm` object. It then tries to populate the model
+with the data from `$_POST` which is provided in Yii through [[yii\web\Request::post()]].
+If the model is successfully populated (i.e., the user has submitted the HTML form),
+it will call [[yii\base\Model::validate()|validate()]] to make sure the data entered
+are valid.
+
+If everything is fine, the action will render a view named `entry-confirm` to confirm
+with the user that the data he has entered is accepted. Otherwise, the `entry` view will
+be rendered, which will show the HTML form together with the validation error messages (if any).
+
+> Info: The expression `Yii::$app` represents the [application](structure-applications.md) instance
+  which is a singleton and is globally accessible through this expression. The application instance
+  is also a [service locator](concept-service-locator.md) providing service components such as `request`,
+  `response`, `db`, etc. In the above code, the `request` component is used to get the `$_POST` data.
+
+
 Creating Views
 --------------
 

framework/helpers/FileHelper.php

@@ -8,7 +8,7 @@
 namespace yii\helpers;
 
 /**
- * Filesystem helper
+ * File system helper
  *
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @author Alex Makarov <sam@rmcreative.ru>