DSQL supports various database vendors natively but also supports 3rd party extensions. For current status on database support see: Vendor support and Extensions.

class Atk4\Data\Persistence\Sql\Connection

Connection class is handy to have if you plan on building and executing queries in your application. It’s more appropriate to store connection in a global variable or global class:

$app->db = Atk4\Data\Persistence\Sql\Connection::connect($dsn, $user, $pass, $defaults);
static Atk4\Data\Persistence\Sql\Connection::connect($dsn, $user = null, $password = null, $defaults = [])

Determine which Connection class should be used for specified $dsn, establish connection to DB by creating new object of this connection class and return.


new Connection

This should allow you to access this class from anywhere and generate either new Query or Expression class:

$query = $app->db->dsql();

// or

$expr = $app->db->expr('show tables');
Atk4\Data\Persistence\Sql\Connection::expr($template, $arguments)

Creates new Expression class and sets Expression::$connection.

  • $arguments (array) – Other default properties for connection class.


new Expression


Creates new Query class and sets Query::$connection.

  • $defaults (array) – Other default properties for connection class.


new Query

Here is how you can use all of this together:

$dsn = 'mysql:host=localhost;port=3307;dbname=testdb';

$connection = Atk4\Data\Persistence\Sql\Connection::connect($dsn, 'root', 'root');

echo 'Time now is: ' . $connection->expr('select now()');

connect will determine appropriate class that can be used for this DSN string. This can be a PDO class or it may try to use a 3rd party connection class.

Connection class is also responsible for executing queries. This is only used if you connect to vendor that does not use PDO.

Atk4\Data\Persistence\Sql\Connection::execute(Expression $expr) \Doctrine\DBAL\Result

Creates new Expression class and sets Expression::$connection.

  • $expr (Expression) – Expression (or query) to execute



Atk4\Data\Persistence\Sql\Connection::registerConnectionClass($connectionClass, $connectionType)

Adds connection class to the registry for resolving in Connection::resolveConnectionClass method.

  • $connectionClass (string) – The connection class to be used for the diver type

  • $connectionType (string) – Alias of the connection

Developers can register custom classes to handle driver types using the Connection::registerConnectionClass method:

Connection::registerConnectionClass(Custom\MySQL\Connection::class, 'pdo_mysql');
Atk4\Data\Persistence\Sql\Connection::connectDbalConnection(array $dsn)

The method should establish connection with DB and return the underlying connection object used by the Connection class. By default PDO is used but the method can be overridden to return custom object to be used for connection to DB.