gistfile1.txt

       $pdo = new \PDO('mysql:dbname=parfetts;host=localhost', '', '');
        $pdo->beginTransaction();
        $statement = $pdo->prepare("INSERT INTO trolley_items ( `trolley_id`,`pack_id`,`price`,`quantity` )
			VALUES
            ( ?, ?, ?, ? )
			ON DUPLICATE KEY UPDATE `quantity` = `quantity` + 1");
        $statement->execute(array($trolleyId, $packId, $price, $quantity));
        $pdo->commit();