$buyList = array(
        array('name' => 'Телевизор', 'price' => '400', 'quantity' => 1),
        array('name' => 'Телефон', 'price' => '300', 'quantity' => 3),
        array('name' => 'Кросовки', 'price' => '150', 'quantity' => 2),
    );

     function resultBuyList($buyList)
     {
        foreach ($buyList  as $key => $value) {
            $credits = $value['quantity'] * $value['price'];
            $creditCount += $credits;
            $productCount += $value['quantity'];
        }
         return $result = "Вы купили $productCount единиц товара, общая сумма к оплате: $creditCount";
    }


     resultBuyList($buyList);