Many DB connections

Question

How do you create multiple DB connections using the Singleton pattern? Or maybe it’s better to come up with to share the same class, but multiple connections?

Answer 1

How to use Factory pattern to return the same instance for each connection, e.g.

ConnectionFactory::getInstance(ConnectionFactory::DEVELOPMENT);

Gets an instance Connectionto connect to the development database.

Connection ConnectionFactory, . , , Connection.

Answer 2

.

java:

http://java.sun.com/developer/onlineTraining/Programming/JDCBook/Code/JDCConnectionPool.java

, .

Answer 3

Singleton, ? Singleton -, , , , . , Singleton PHP .

Answer 4

, , , , - :

interface Connection_Interface
{
    public function connect();
    public function disconnect();
    public function exec($sql);
    // etc...
}

class Connection implements Connection_Interface
{
    public function __construct($host, $username, $password, $database);
    public function connect();
    public function disconnect();
    public function exec($sql);
    // etc...
}

, :

class Connection_Multiple implements Connection_Interface
{
    protected $_connections = array();        

    public function __construct();
    public function add(Connection $connection);
    public function connect();
    public function disconnect();
    public function exec($sql)
    {
        // decide here which connection you want to use, then...
        return $connection->exec($sql);
    }
    // etc...
}

Since both a single connection and several connection classes implement the same interface, you can use either the exact same way.

Answer 5

I came up with this solution:

class Database {
    private static $instances = array();

    public static function getInstance($connection='default') {
        if (!array_key_exists($connection,self::$instances)) {
            self::$instances[$connection] = new Database($connection);
        }
        return self::$instances[$connection];
    }

    private function __construct($connection) {
        $this->credentials = // getting credentials from config by $connection...
        $this->connect(); // connect using credentials
    }
}

$DB1 = Database::getInstance('development');
$DB2 = Database::getInstance('production');

It seems to work for me. Is this a Singleton pattern or something mixed?