Introduction to the use of the association model of PHP Yii2 framework

Active RecordRelevant data can be clustered so that it can be easily accessed through the original data. For example, customer data is related to order data because a customer may have already stored one or more orders. This relationship is declared appropriately, you can use$customer->ordersThe expression accesses the customer's order information. This expression will return the containingOrder Active RecordAn array of customer order information for instance.

Declare an association

You must firstActive RecordDefine an association in a class to useActive Recordassociated data. Simply declare an association method for each need to define an association relationship, as shown below,

class Customer extends ActiveRecord
{
    // ...
    public function getOrders()
    {
        return $this->hasMany(Order::className(), ['customer_id' => 'id']);
    }
}
class Order extends ActiveRecord
{
    // ...
    public function getCustomer()
    {
        return $this->hasOne(Customer::className(), ['id' => 'customer_id']);
    }
}

In the above code, weCustomerThe class declares aordersAssociate, and asOrderA statementcustomerRelated.

Each association method must be named like this:getXyz. Then we passxyz(lowercase of the initial letter) Call this association name. Please note that the association name is case sensitive.

When declaring an association, the following information must be specified:

• Corresponding relationship: by callinghasMany()orhasOne()Specified. In the example above, you can easily see such an association statement: A customer can have many orders, and each order has only one customer.
• RelatedActive RecordClass name: used to specifyhasMany()orhasOne()The first parameter of the method. The recommended method is to callXyz::className()to get the string of the class name so that you can use the IDE's automatic completion and make error detection in the compilation phase take effect.
• The associated columns of two sets of data: used to specify the columns related to the two sets of data (hasOne()/hasMany()the second parameter of ). The value of the array is filled in the column of the main data (the associated one is currently declaredActive Recordclass is the main data), and the keys of the array need to be filled in the columns of the relevant data.

A simple formula, first attach the primary key of the table, and then the primary key of the table. As in the example above,customer_idyesOrderattributes, andidyesCustomerattributes. (Translator's note:hasMany()The second parameter of this array key and value order should not be reversed)

Access associated data

After defining the association relationship, you can access the corresponding association data through the association name. Just like accessing an object defined by an associated method, please see the properties for specific concepts. Therefore, now we can call it an associated property.

// SELECT * FROM `customer` WHERE `id` = 123
$customer = Customer::findOne(123);
// SELECT * FROM `order` WHERE `customer_id` = 123
// $orders is an array composed of the Order class$orders = $customer->orders;

Tip: When you passgettermethodgetXyz()A statement calledxyzYou can access the associated properties like the propertiesxyz. Note that this naming is case sensitive.

If usinghasMany() Declare an association relationship, accessing this association property will return the relatedActive Recordarray of instances; if usinghasOne()Declare an association relationship, accessing this association property will return the relatedActive RecordIf no relevant data is found, it will returnnull。

When you first access the associated property, SQL statements are executed to get the data, as shown in the above example. If the same property is accessed again, the previous result will be returned without the SQL statement being re-executed. To force re-execute SQL statements, you should firstunsetThis associated attribute, such as:unset($ customer-> orders)。

$customer->orders; // Get an array of `Order` objects$customer->getOrders(); // Return an instance of ActiveQuery class

Set an alias

class Order extends ActiveRecord
{
    // ...
    public function getCustomer()
    {
        return $this->hasOne(Customer::className(), ['id' => 'customer_id'])->alias('c');
    }
}

Related Query

$order = Order::find()->joinWith('customer')
            ->where(['filter1'=>$filter1, 'filter2'=>$filter2])
            ->andWhere(['=', 'c.filter3', $filter3])
            ->andWhere(['<=', 'cfilter4', $filter4])
            ->one();

This is the article about the introduction to the use of the associated model of the PHP Yii2 framework. For more related PHP Yii2 correlation model content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!