Yii2 Module with different database

Question

I want to combine two applications. One of these as module. There are two different databases. The Module use another database as the base appliaction.

I have created the db connection, which is a component in config.php

return [
    'class' => 'yii\db\Connection',
    'dsn' => 'mysql:host=localhost;dbname=test_db',
    'username' => 'root',
    'password' => '',    
    'charset' => 'utf8',
];

And I have created an ModuleActiveRecord Class which overwrites the Active Record function getDB():

class ModuleActiveRecord extends ActiveRecord
{
    public static function getDb()
    {
        $db = Yii::$app->controller->module->db;
        return Yii::createComponent($db);
}

I get the error message: The table does not exist. Anyone an idea??

Answer 1

You can add multiple database connections like the other answers, for example: db/db_for_module.

You can also configure the module like I do(Example using Yii2 advanced template):

// in common/config/main.php
[
    'db' => [
        'class' => 'yii\db\Connection',
        'dsn' => 'mysql:host=localhost;dbname=test_db',
        'username' => 'root',
        'password' => '123456',    
        'charset' => 'utf8',
    ],
    'modules' => [
        'v1' => [
            'class' => \frontend\modules\v1\Module::class,
            // Increase the component configuration of the module
            'components' => [
                'db' => [
                    'class' => 'yii\db\Connection',
                    'dsn' => 'mysql:host=localhost;dbname=test_db_for_module',
                    'username' => 'root',
                    'password' => '111111',    
                    'charset' => 'utf8',
                ],
            ],
        ],
    ],
]

Definition of v1 module

// in frontend/modules/Module.php
<?php

namespace frontend\modules\v1;

/**
 * v1 module definition class.
 */
class Module extends \yii\base\Module
{
    /**
     * {@inheritdoc}
     */
    public $controllerNamespace = 'frontend\modules\v1\controllers';
}

However, you have to call the db component in a special way in the module's code, for example:

// in frontend/modules/v1/controllers/TestController.php
<?php

namespace frontend\modules\v1\controllers;

/**
 * Test Controller
 */
class TestController extends \yii\web\Controller {

    public function actionTest()
    {
        \Yii::$app->modules['v1']->db->createCommand(...); // This db points to the db connection of this module configuration
        // or
        $this->module->db->createCommand(...) // This db points to the db connection of this module configuration
    }
}

The benefits of doing this:

• You can use the same name: db (if this is what you expect, although it's called in a special way)
• The code other than this module can't see the configuration about this db.
• Even if you don't have a special db connection for this module, you can still call the default db connection correctly using the above method (maybe this is not what you expect)
• Can clearly indicate that a special db connection configuration is used here

Note: This is just a way to override the application default components in the module for reference. I have not practiced this method, but I have tested this is feasible.

Answer 2

Copy the db connection file and import both connections in config (web.php):

'components' => [
    ...
    'db' => require(__DIR__ . '/db.php'),
    'db_copy' => require(__DIR__ . '/db_copy.php'),
]

Then override the db connection in the ActiveRecord which uses the copy db like this:

public static function getDb()
{
    return Yii::$app->get('db_copy');
}