How to use multiple database connections in CakePHP?

CakePHP is a popular PHP development framework that provides the basic functionality and structure needed to quickly develop web applications. In modern applications, it has become a common requirement to use multiple database connections, for example, to establish a master-slave database connection or to shard data into different databases. This article will introduce how to use multiple database connections in CakePHP.

Default database connection in CakePHP

Before we begin, let us first understand the default database connection in CakePHP. CakePHP uses configuration files to manage database connection information, which is usually stored in the config/app.php file. This file contains a configuration array, in which database connection configuration information can be set in the default subkey of the array.

By default, CakePHP uses MySQL as the primary database connection. The following is a sample code:

    'Datasources' => [
        'default' => [
            'className' => 'CakeDatabaseConnection',
            'driver' => 'CakeDatabaseDriverMysql',
            'persistent' => false,
            'host' => 'localhost',
            'username' => 'myuser',
            'password' => 'mypass',
            'database' => 'mydb',
            'encoding' => 'utf8mb4',
            'timezone' => 'UTC',
            'cacheMetadata' => true,
            'quoteIdentifiers' => false,
            'log' => false,
        ],
    ],

In the above configuration information, we can see several general items, such as the class name of the database connection, driver type, user name and password, etc.

Using multiple database connections

To use multiple database connections, we can create a new database connection by copying the default subkey above. For example, the following code creates a new connection named secondary:

    'Datasources' => [
        'default' => [
            'className' => 'CakeDatabaseConnection',
            'driver' => 'CakeDatabaseDriverMysql',
            '...
        ],
        'secondary' => [
            'className' => 'CakeDatabaseConnection',
            'driver' => 'CakeDatabaseDriverPostgres',
            'persistent' => false,
            'host' => 'localhost',
            'username' => 'myuser',
            'password' => 'mypass',
            'database' => 'mydb2',
            'encoding' => 'utf8',
            'timezone' => 'UTC',
            'cacheMetadata' => true,
            'quoteIdentifiers' => false,
            'log' => false,
        ],
    ],

In the above code, we can see the new connection configuration items, including different class names, driver types, user names and passwords, etc. . Please note that for example, for sensitive information such as username and password, we should use the encrypt() and decrypt() functions in the Crypt class to encrypt and decrypt.

Using different connections

Now that we have set up multiple database connections, the next step is to use them in the application. In CakePHP, we can use the ConnectionManager class to access different connections. The following is the sample code:

// 使用默认连接
$users = TableRegistry::get('Users');

// 使用secondary连接
$secondaryConn = ConnectionManager::get('secondary');
$secondaryUsers = TableRegistry::get('Users', [
    'connection' => $secondaryConn
]);

In the above code, we can see how we use the ConnectionManager class to obtain different connections. Once we have the connection, we can use the TableRegistry class to get the data table object associated with the connection. For the default connection, we can omit not passing the connection option.

Extending the use of connections

When making use of connections, we can further extend it to meet the needs of the application. For example, we can create a custom connection class by inheriting CakePHP's database connection class so that we can better handle connections. The following is a sample code:

class CustomMySqlConnection extends MySqlConnection
{
    public function __construct($config)
    {
        parent::__construct($config);
        $this->_isCustom = true;
    }

    public function customFunction()
    {
        return "Hello from CustomMySqlConnection!";
    }
}

// 使用CustomMySqlConnection来创建连接
'custom' => [
    'className' => 'CustomMySqlConnection',
    'driver' => 'CakeDatabaseDriverMysql',
    '...
],

// 获取custom连接并调用自定义函数
$customConn = ConnectionManager::get('custom');
$customConn->customFunction();

In the above code, we created a class named CustomMySqlConnection to extend the default MySqlConnection class in CakePHP. This class adds a custom function and sets the _isCustom variable to true so that we can distinguish it from the original connection in the application.

Conclusion

By using the above methods, we can easily set up and use multiple database connections in CakePHP to support complex application requirements. Although these connections look very similar, using the ConnectionManager and TableRegistry classes to obtain and manipulate them gives us the flexibility to use and manage them in our applications.

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