**Course Title:** Mastering Yii Framework: Building Scalable Web Applications **Section Title:** Introduction to Yii and Development Environment **Topic:** Exploring Yii's directory structure and configuration files **Overview** In this topic, we will delve into the directory structure and configuration files of the Yii framework. Understanding these components is crucial for building scalable and maintainable web applications with Yii. By the end of this topic, you will have a clear grasp of the directory structure and configuration files, enabling you to create and manage your own Yii projects efficiently. **Directory Structure** A typical Yii project directory structure is organized as follows: ```bash app/ backend/ assets/ config/ controllers/ models/ runtime/ views/ common/ config/ mail/ models/ components/ frontend/ assets/ config/ controllers/ models/ runtime/ views/ vendor/ web/ assets/ index.php yii/ config composer.json ``` Let's break down the key directories and their purposes: * `app/`: This directory contains the main application code. * `backend/`, `frontend/`, and `common/`: These directories store the backend, frontend, and shared application logic, respectively. * `vendor/`: This directory stores third-party dependencies installed via Composer. * `web/`: This directory serves as the document root for the application. * `config/`: This directory contains configuration files for the application. **Configuration Files** Configuration files in Yii are used to store settings and parameters for the application. The main configuration files are: * `config/web.php`: This file contains the main configuration settings for the application, including database connections, component configurations, and module configurations. * `config/console.php`: This file contains configuration settings for the console application. * `config/params.php`: This file stores parameters that can be accessed throughout the application. A basic `config/web.php` file might look like this: ```php use yii\web\Application; $params = require __DIR__ . '/params.php'; $config = [ 'id' => 'basic', 'basePath' => dirname(__DIR__), 'bootstrap' => ['log'], 'defaultRoute' => 'site/index', 'components' => [ 'request' => [ 'enableCookieValidation' => true, 'cookieValidationKey' => 'your secret key here', ], 'cache' => [ 'class' => 'yii\caching\FileCache', ], 'user' => [ 'identityClass' => 'app\models\User', 'enableAutoLogin' => true, ], 'errorHandler' => [ 'errorAction' => 'site/error', ], ], 'params' => $params, ]; return $config; ``` This configuration file sets up the basic application settings, including the request and cache components, user authentication, and error handling. **Environment Variables** Yii provides support for environment variables through the `params.php` file. This file can store settings that are specific to different environments, such as development, staging, or production. For example, you can define environment variables for the database connection: ```php return [ 'db.host' => getenv('DB_HOST'), 'db.username' => getenv('DB_USERNAME'), 'db.password' => getenv('DB_PASSWORD'), 'db.name' => getenv('DB_NAME'), ]; ``` You can then access these variables in your application using the `Yii::$app->params` property: ```php $dbHost = Yii::$app->params['db.host']; ``` **Conclusion** In this topic, we explored the directory structure and configuration files of the Yii framework. We covered the key directories and their purposes, as well as the main configuration files and their contents. We also discussed environment variables and how to access them in your application. **What's Next?** In the next topic, we will dive into routing in Yii, covering URL management, route configuration, and creating custom routes. **External Resources** * Yii Framework Documentation: [https://www.yiiframework.com/doc-2.0/index.html](https://www.yiiframework.com/doc-2.0/index.html) * Yii 2.0 Configuration Guide: [https://www.yiiframework.com/doc-2.0/guide-index.html#configuration](https://www.yiiframework.com/doc-2.0/guide-index.html#configuration) **Leave a Comment or Ask for Help** If you have any questions or need further clarification on any of the topics covered in this section, feel free to leave a comment below.