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How to Program With Yii2: User Access Controls

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Difficulty:IntermediateLength:MediumLanguages:
This post is part of a series called How to Program With Yii2.
How to Program With Yii2: Localization With I18n
How to Program With Yii2: Rich Text Input With Redactor
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What You'll Be Creating

If you're asking, "What's Yii?" check out my earlier tutorial: Introduction to the Yii Framework, which reviews the benefits of Yii and includes an overview of what's new in Yii 2.0, released in October 2014.

In this Programming With Yii2 series, I'm guiding readers in use of the newly upgraded Yii2 Framework for PHP. 

In part one, we set up Yii2 locally, built a Hello World application, set up a remote server and used Github to deploy our code. In part two, we learned about Yii's implementation of its Model View Controller architecture and how to build web pages and forms that collect and validate data. 

In part three, we used Yii's database and active record capabilities to automate code generation for a basic web application. In part four, we learned how to integrate user registration. And in part five, we explored localization with I18n to prepare your application for global users. 

In this tutorial, I'm going to show you how to implement access controls to ensure that only the right users can access the parts of our application that we wish them to.

For these examples, we'll continue to imagine we're building a framework for posting simple status updates, e.g. our own mini-Twitter.

Just a reminder, I do participate in the comment threads below. I'm especially interested if you have different approaches, additional ideas, or want to suggest topics for future tutorials.

What Is Access Control?

Access control integrates with the framework's authentication features to allow or restrict access to specific features or pages of your website. 

The code we've written thus far allows anyone to create posts even if they haven't signed in. For example, in our sample application, you can visit the Status page and post items without signing in. 

We can use Yii2's simple access control features to ensure that users register and sign in before adding and viewing status posts. 

Yii2 also offers more advanced (and complex) Role Based Access Control (RBAC) which we will not be implementing at this time. With RBAC, you define a sophisticated hierarchy of permissions for each possible activity within your application.

Yii2's built in Access Control supports only two roles by default: guest (not logged in), represented by '?', and authenticated, represented by '@'. With simple access controls, we can just limit access to specific pages or controller actions based on the login state. If users are not logged in when they visit the place pages, Yii will redirect them to the login page.

In this tutorial, I'll introduce you to using Yii2's simple access controls for our sample application. Then we'll extend simple access with additional roles such as moderator and administrator.

Implementing Simple Access Controls

Currently, our application allows access to the StatusController even without signing in. Let's fix that.

Status Controller Open access to anything regardless of login state

The framework makes it quite simple to implement these controls. We just add behaviors to StatusController.php which define the access rules for each action, e.g. index, create, view, etc. 

Here we'll review the access behavior but if you're interested, Yii's verb filters allow you to restrict http request operations based on your controller action.

Once added, if you click the Status menu, you'll be redirected to the login page:

StatusController Redirect to Login Page with Access Control

Yii also handles the redirect back to the Status index page once login is complete.

Adding Model Ownership

Now, when users access the Status pages, we can find the current user with this code:

Yii::$app->user->getId();

And we can associate Status posts with their creator in the model.

In order to do this, we have to extend the Status table with a new table migration:

Here's the migration code which adds a column for created_by. We also add a foreign key to create a relation between the Status->created_by field and the User->id table.

Let's run the migration:

I re-ran the Gii code generation with the new Status table and copied and pasted the new additional elements. Most were minor but you'll notice it adds a new ActiveQuery for the relation:

So, just before new status items are saved, we can update the created_by field to the currently logged in user. And we can trust access controls to ensure the create method is accessed only by authenticated users:

We'll also extend the view widget to include the created_by field:

Status Detail View Showing Created By User Id

We can also use the created_by relation to display the email address:

The createdBy.email accesses the Status::getCreatedBy relation method. This displays the user's email address:

However, in order to support this capability with the Yii2-user extension we implemented in part four, we had to make two modifications. First, in our app\config\web.php configuration array, we added a model override to app\models\User.php:

We also created this model in app\models:

These two changes provided support for the relation.

Extending Simple Access Controls

What if we wanted to have additional capability around controller actions? For example, what if we want to restrict delete operations to moderators or administrators? Yii2's simple access control doesn't have a moderator or administrator concept unless you create one with RBAC.

Note that Yii2-user extension does have an admin identifier for specific users, but it too lacks the flexibility for additional roles.

The Code Ninja wrote up a nice example of extending simple access controls to support moderators and administrators (Simpler Role Based Authorization in Yii 2.0) without having to resort to using RBAC. Their example works with the Yii2 advanced application template. 

Our application is different in that we're using Yii's basic application template and we're using the Yii2-user extension. Therefore, I've made some changes to their guide:

First, we create an app\components directory and and an AccessRule.php file which extends Yii's built-in AccessRule model:

Then, we add role definitions to our app\models\User model:

Yii2-user doesn't implement the role column when creating new users. So you can either specify roles for moderators and administrators manually in MySQL or later build your own web user interface for granting roles.

In vendor\dektrium\yii2-user\models\RegistrationForm.php, I added this line to define the user role for default users:

Note: you'll have to make this change manually if you want it because my vendor directory doesn't get checked in to our GitHub tree—and yes, there is probably a more elegant way to do this in the core codebase after registration occurs, e.g. extend the createUser method in app/models/User.php. Best practice may be to fork the vendor repository and bring it into your own code tree.

Finally, in StatusController.php, we add some libraries and these access definitions. In the example below, update actions are restricted to moderators and delete actions are restricted to administrators.

Now, when you log out and visit the Status page from the navigation bar, you'll be taken to the login screen:

Login Access Restriction

When you sign in, you'll be sent to the index view again:

Authenticated View of Status Index Page

However, if I click Delete, I will get this access forbidden error—because I'm a lowly user, not an administrator:

Access Forbidden Due to User Role

If you want to elevate yourself to administrator, you can do so in the database, changing the User table's role column for your user_id to 20 for moderator and 30 for admin. Try the update and delete operations again and you'll be permitted depending on your chosen role.

Access controls are one of the many features that make me a huge advocate for using the Yii Framework. Yii makes me a much more efficient developer, capable of delivering solutions much more quickly than I can with vanilla PHP.

What's Next?

Watch for upcoming tutorials in my Programming With Yii2 series as I continue diving into different aspects of the framework. You may also want to check out my Building Your Startup With PHP series, which is using Yii2's advanced template as I build a real world application.

If you'd like to know when the next Yii2 tutorial arrives, follow me @reifman on Twitter or check my instructor page. My instructor page will include all the articles from this series as soon as they are published. You can also email me at my Lookahead Consulting website.

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