**Course Title:** Mastering Yii Framework: Building Scalable Web Applications **Section Title:** Database Management with Active Record **Topic:** Using Active Record for database interactions **Overview** In this topic, we will explore the Active Record pattern, a fundamental concept in Yii's database management. Active Record provides a simple and intuitive way to interact with databases, making it easier to perform CRUD (Create, Read, Read, Update, Delete) operations. By the end of this topic, you will understand how to use Active Record to perform database interactions and be well-prepared to tackle more complex database operations. **What is Active Record?** Active Record is a design pattern that maps a database table to a class in your application. This class, known as the Active Record class, encapsulates the interactions with the database table, providing a simple and intuitive way to perform CRUD operations. **Key Concepts** Before we dive into the details, let's cover some key concepts: * **Model**: A Model is a class that represents a database table. In Yii, Models are typically created using the `yii\db\ActiveRecord` class. * **Attributes**: Attributes are the columns of a database table. In Yii, attributes are accessed using getter and setter methods. * **Validation**: Validation is the process of checking if the data being inserted or updated is valid. In Yii, validation is performed using rules defined in the Model class. **Creating an Active Record Class** To create an Active Record class, you need to extend the `yii\db\ActiveRecord` class and define the attributes of the database table. Here's an example: ```php namespace app\models; use yii\db\ActiveRecord; class User extends ActiveRecord { public static function tableName() { return 'users'; } public function rules() { return [ [['name', 'email'], 'required'], [['email'], 'email'], [['name'], 'string', 'max' => 255], ]; } public function attributeLabels() { return [ 'id' => 'ID', 'name' => 'Name', 'email' => 'Email', ]; } } ``` In this example, we've created a `User` class that extends the `ActiveRecord` class. We've defined the `tableName()` method to specify the database table name, and the `rules()` method to define the validation rules for the attributes. **Performing CRUD Operations** Now that we have an Active Record class, we can perform CRUD operations using the following methods: * `find()`: Retrieves a list of records from the database table. * `findOne()`: Retrieves a single record from the database table. * `create()`: Creates a new record in the database table. * `update()`: Updates an existing record in the database table. * `delete()`: Deletes a record from the database table. Here's example of how to use these methods: ```php // Retrieve a list of records $users = User::find()->all(); // Retrieve a single record $user = User::findOne(1); // Create a new record $user = new User(); $user->name = 'John Doe'; $user->email = 'john.doe@example.com'; $user->save(); // Update an existing record $user = User::findOne(1); $user->name = 'Jane Doe'; $user->save(); // Delete a record $user = User::findOne(1); $user->delete(); ``` **Conclusion** In this topic, we've covered the basics of Active Record, a fundamental concept in Yii's database management. We've created an Active Record class, defined the attributes and validation rules, and performed CRUD operations using the `find()`, `findOne()`, `create()`, `update()`, and `delete()` methods. By mastering Active Record, you'll be well-prepared to tackle more complex database operations and build scalable web applications using the Yii framework. **What's Next?** In the next topic, we'll explore how to perform CRUD operations using Active Record in more detail, including how to use scopes, behaviors, and events to customize the behavior of your Active Record classes. **Leave a comment or ask for help** If you have any questions or need help with implementing Active Record in your application, please leave a comment below. I'll do my best to assist you. **External Resources** For more information on Active Record, please refer to the following resources: * [Yii Framework Documentation: Active Record](https://www.yiiframework.com/doc/guide/2.0/en/db-active-record) * [Yii Framework Documentation: Model](https://www.yiiframework.com/doc/guide/2.0/en/model) * [Yii Framework Documentation: Validation](https://www.yiiframework.com/doc/guide/2.0/en/input-validation)

namespace app\models;

use yii\db\ActiveRecord;

class User extends ActiveRecord
{
    public static function tableName()
    {
        return 'users';
    }

    public function rules()
    {
        return [
            [['name', 'email'], 'required'],
            [['email'], 'email'],
            [['name'], 'string', 'max' => 255],
        ];
    }

    public function attributeLabels()
    {
        return [
            'id' => 'ID',
            'name' => 'Name',
            'email' => 'Email',
        ];
    }
}

// Retrieve a list of records
$users = User::find()->all();

// Retrieve a single record
$user = User::findOne(1);

// Create a new record
$user = new User();
$user->name = 'John Doe';
$user->email = 'john.doe@example.com';
$user->save();

// Update an existing record
$user = User::findOne(1);
$user->name = 'Jane Doe';
$user->save();

// Delete a record
$user = User::findOne(1);
$user->delete();