yii2-bootstrap/docs/guide/controller.md

Controller

Controller is one of the key parts of the application. It determines how to handle incoming request and creates a response.

Most often a controller takes HTTP request data and returns HTML, JSON or XML as a response.

Basics

Controller resides in application's controllers directory is is named like SiteController.php where Site part could be anything describing a set of actions it contains.

The basic web controller is a class that extends \yii\web\Controller and could be very simple:

namespace app\controllers;

use yii\web\Controller;

class SiteController extends Controller
{
	public function actionIndex()
	{
		// will render view from "views/site/index.php"
		return $this->render('index');
	}

	public function actionTest()
	{
		// will just print "test" to the browser
		return 'test';
	}
}

As you can see, typical controller contains actions that are public class methods named as actionSomething. The output of an action is what the method returns. The return value will be handled by the response application component which can convert the output to differnet formats such as JSON for example. The default behavior is to output the value unchanged though.

Routes

Each controller action has a corresponding internal route. In our example above actionIndex has site/index route and actionTest has site/test route. In this route site is referred to as controller ID while test is referred to as action ID.

By default you can access specific controller and action using the http://example.com/?r=controller/action URL. This behavior is fully customizable. For details refer to URL Management.

If controller is located inside a module its action internal route will be module/controller/action.

In case module, controller or action specified isn't found Yii will return "not found" page and HTTP status code 404.

Note: If controller name or action name contains camelCased words, internal route will use dashes i.e. for DateTimeController::actionFastForward route will be date-time/fast-forward.

Defaults

If user isn't specifying any route i.e. using URL like http://example.com/, Yii assumes that default route should be used. It is determined by \yii\web\Application::defaultRoute method and is site by default meaning that SiteController will be loaded.

A controller has a default action. When the user request does not specify which action to execute by using an URL such as http://example.com/?r=site, the default action will be executed. By default, the default action is named as index. It can be changed by setting the \yii\base\Controller::defaultAction property.

Action parameters

It was already mentioned that a simple action is just a public method named as actionSomething. Now we'll review ways that an action can get parameters from HTTP.

Action parameters

You can define named arguments for an action and these will be automatically populated from corresponding values from $_GET. This is very convenient both because of the short syntax and an ability to specify defaults:

namespace app\controllers;

use yii\web\Controller;

class BlogController extends Controller
{
	public function actionView($id, $version = null)
	{
		$post = Post::find($id);
		$text = $post->text;

		if ($version) {
			$text = $post->getHistory($version);
		}

		return $this->render('view', [
			'post' => $post,
			'text' => $text,
		]);
	}
}

The action above can be accessed using either http://example.com/?r=blog/view&id=42 or http://example.com/?r=blog/view&id=42&version=3. In the first case version isn't specified and default parameter value is used instead.

Getting data from request

If your action is working with data from HTTP POST or has too many GET parameters you can rely on request object that is accessible via \Yii::$app->request:

namespace app\controllers;

use yii\web\Controller;
use yii\web\HttpException;

class BlogController extends Controller
{
	public function actionUpdate($id)
	{
		$post = Post::find($id);
		if (!$post) {
			throw new NotFoundHttpException;
		}

		if (\Yii::$app->request->isPost) {
			$post->load($_POST);
			if ($post->save()) {
				$this->redirect(['view', 'id' => $post->id]);
			}
		}

		return $this->render('update', ['post' => $post]);
	}
}

Standalone actions

If action is generic enough it makes sense to implement it in a separate class to be able to reuse it. Create actions/Page.php

namespace app\actions;

class Page extends \yii\base\Action
{
	public $view = 'index';

	public function run()
	{
		return $this->controller->render($view);
	}
}

The following code is too simple to implement as a separate action but gives an idea of how it works. Action implemented can be used in your controller as following:

public SiteController extends \yii\web\Controller
{
	public function actions()
	{
		return [
			'about' => [
				'class' => 'app\actions\Page',
				'view' => 'about',
			],
		];
	}
}

After doing so you can access your action as http://example.com/?r=site/about.

Action Filters

Action filters are implemented via behaviors. You should extend from ActionFilter to define a new filter. To use a filter, you should attach the filter class to the controller as a behavior. For example, to use the AccessControl filter, you should have the following code in a controller:

public function behaviors()
{
    return [
        'access' => [
            'class' => 'yii\web\AccessControl',
            'rules' => [
                ['allow' => true, 'actions' => ['admin'], 'roles' => ['@']],
            ),
        ),
    );
}

In order to learn more about access control check authorization section of the guide. Two other filters, PageCache and HttpCache are described in caching section of the guide.

Catching all incoming requests

TBD

See also

• Console