What are controllers in Yii, and what is their purpose?
Jul 13, 2025 am 12:50 AM
In Yii, the controller coordinates application logic by processing user requests, interactive models, and rendering views. The main responsibilities of the controller include: ① Processing HTTP requests; ② Interacting with the model to obtain or save data; ③ Deciding which view to display and pass data; ④ Processing form submissions; ⑤ Returning HTML, JSON, or redirection responses. The Yii controller is usually inherited from yii\web\Controller, and each public method corresponds to an action that can be accessed through the URL. For example, visiting http://example.com/site/index will call the actionIndex() method of SiteController. Common tasks include validating input, calling models, rendering views, redirecting, and returning JSON responses. Development recommendations include keeping the controller concise, using filters, organizing actions reasonably, using namespaces correctly, and returning appropriate HTTP status codes. Controllers help to achieve maintainability and scalability of code and are an important part of the MVC architecture.
In Yii, controllers are the central part of handling user requests. They act as a middleman between models (data) and views (what users see). When you visit a page in a Yii application, the URL determines which controller and action to run, and based on that, it fetches data or performs operations, then returns the appropriate response—like displaying a page or sending JSON.
What Does a Controller Do?
A controller's main job is to process incoming HTTP requests and decide what to do with them. This usually involves:
- Interacting with models to get or save data
- Deciding which view to display
- Passing data to views
- Handling form submissions
- Returning different types of responses (HTML, JSON, redirects)
Controllers help organize your code by grouping related actions together. For example, a PostController might handle all actions related to blog posts—viewing, creating, editing, deleting.
Structure of a Controller in Yii
In Yii, a controller is typically a PHP class that extends yii\web\Controller . Each public method in that class is called an action , and each action can be accessed via a URL.
For example, if you have a controller named SiteController.php , and inside it there's a method called actionIndex() , you can access that action using a URL like:
http://example.com/index.php?r=site/index
Here:
-
sitereferers toSiteController -
indexrefers toactionIndex
You can also use pretty URLs with URL rewriting enabled, making the URL cleaner:
http://example.com/site/index
Common Tasks Controllers Handle
Here are some typical things you'll find a controller doing:
- Validating input from forms or API requests
- Calling model methods to retrieve or update data
- Rendering views with dynamic content
- Redirecting users after an action (like submitting a form)
- Returning JSON responses for AJAX calls
Let's say you're building a simple blog. In your PostController , you might have:
public function actionView($id)
{
$post = Post::findOne($id);
if (!$post) {
throw new NotFoundHttpException('The requested post does not exist.');
}
return $this->render('view', ['post' => $post]);
}This action:
- Gets the
$idparameter from the URL - Fetches the post from the database
- Throws an error if it doesn't exist
- Renders the
viewtemplate and passes the post data to it
Tips for Working with Controllers
- Keep controllers lean: Don't put too much logic directly in controllers. Use models or services for heavy lifting.
- Use filters for common tasks like authentication: Yii supports filters like
accessControlandverbControl. - Organize actions logically: Group related actions into the same controller.
- Use controller namespaces properly: Especially when working with modules or advanced templates.
- Return proper HTTP status codes: Helps with SEO and APIs.
Controllers are essential in any MVC framework like Yii because they manage how users interact with your app. While it's possible to write everything in one place, using controllers keeps your code clean, maintainable, and scalable.
Basically that's it.
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