protected static function _connection(& $connection)
	{
		if (static::isString($connection))
			$connection = static::connection($connection);

		if (!$connection instanceof \PDO)
			throw new \InvalidArgumentException("invalid connection");
	}
protected static function _connection(& $connection)
	{
		if (static::isString($connection))
			$connection = static::connection($connection);

		if (!$connection instanceof \PDO)
			throw new \InvalidArgumentException("invalid connection");
	}
protected static function _connection ( & $ connection ) { if ( static :: isString ( $ connection ) ) $ connection = static :: connection ( $ connection ) ; if ( ! $ connection instanceof \ PDO ) throw new \ InvalidArgumentException ( "invalid connection" ) ; }
Transform the connection into a PDO instance. Throw if the connection is invalid or isn't registered.

@category Internal Functions

@param string,PDO $connection the database connection name or PDO instance

@return void
Transform the connection into a PDO instance . Throw if the connection is invalid or isn t registered .