What are models in Yii, and what is their purpose?
Jul 21, 2025 am 01:53 AM
In Yii, the model is used to process data logic, verify input, represent database table structure, and support business logic and non-database forms. 1. The model defines verification rules through the rules() method to ensure that user input meets the requirements; 2. Use Active Record class to map database tables to realize data addition, deletion, modification and search operations; 3. You can add business methods such as isSubscribed() and behavioral extension functions such as TimestampBehavior; 4. Supports a form model that does not depend on the database, which is suitable for contact forms, search forms and other scenarios, improving code organization and maintainability.
In Yii, models are the components responsible for handling data logic and representing the structure of your application's data. They're a core part of the MVC (Model-View-Controller) architecture that Yii follows. The main purpose of models is to manage data, validate user input, and interact with the database — but they can also be used for other data-related tasks like formatting or business logic.
What Do Models Typically Handle?
A model in Yii usually corresponds to a single table or structure in your database. It handles things like:
- Retrieving and saving data
- Validating form inputs
- Defining rules and behaviors
- Managing relationships between different data types
This keeps your controllers clean and focused on request handling, not data manipulation.
1. Handling Data Validation and Input
One of the most common uses of models in Yii is validating user input. For example, when you have a form for creating a new user, the model defines what fields are required, what formats they should follow, and any custom validation rules.
Here's how it typically works:
- You define validation rules inside the
rules()method of your model. - When a form is submitted, Yii automatically checks these rules before saving data.
- If validation fails, errors are returned so users can correct their input.
public function rules()
{
Return [
[['username', 'email', 'password'], 'required'],
['email', 'email'],
['username', 'string', 'max' => 255],
];
}This helps centralize validation logic and ensures consistent behavior across your app.
2. Representing Database Tables
Models often represent a specific table in the database. In Yii, this is usually done using Active Record classes, which extend yii\db\ActiveRecord .
Each model class is tied to a specific table through the tableName() method:
public static function tableName()
{
return 'user';
}Once set up, you can perform operations like:
- Fetching records:
User::findOne($id) - Saving changes:
$user->save() - Deleting records:
$user->delete()
This makes working with databases much more intuitive and object-oriented.
3. Adding Business Logic and Custom Behaviors
Beyond just storing and retrieving data, models are a great place to put business logic. For instance, if a user has a subscription, you might add a method like isSubscribed() directly in the User model.
You can also attach behaviors to models — such as timestamps, soft deletes, or audit trails — using Yii's behavior system. This keeps your code modular and reusable.
For example, adding automatic timestamps:
public function behaviors()
{
Return [
'timestamp' => [
'class' => 'yii\behaviors\TimestampBehavior',
'value' => new \yii\db\Expression('NOW()'),
],
];
}This way, you don't have to manually update created/updated times every time.
4. Supporting Form Models Without Databases
Not all models need to connect to a database. Yii also supports form models — sometimes called "model-only" or "standalone" models — which are useful for forms that don't map directly to a table.
These models still use the same validation features but don't inherit from ActiveRecord . Instead, they extend yii\base\Model .
Use cases include:
- Contact forms
- Search forms
- Settings configuration forms
They're especially helpful when you want to collect and validate data that isn't stored directly in the database.
So, models in Yii play a key role in managing data flow and logic. Whether you're dealing with database records, complex validation, or standalone forms, putting that logic into models keeps your code organized and maintained. Basically, they're where your data lives — and where you make sure it behaves properly.
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