我有產品價格的歷史列表（按created_at排序），如下所示：Array( [0] => stdClass Object ( [id] => 1 [product_id] => 49 [price] => 14520000.0000 [created_at] => 1592501154 ) [1] => stdClass Object ( [id] => 2 [product_id] => 49 [price] => 14000000.0000 [created_at] => 1592587554 ) [2] => stdClass Object ( [id] => 4 [product_id] => 49 [price] => 14800000.0000 [created_at] => 1592673954 ) [3] => stdClass Object ( [id] => 5 [product_id] => 49 [price] => 10000000.0000 [created_at] => 1592760354 ) [4] => stdClass Object ( [id] => 6 [product_id] => 49 [price] => 14000000.0000 [created_at] => 1592846754 ) [5] => stdClass Object ( [id] => 7 [product_id] => 49 [price] => 14000000.0000 [created_at] => 1592933154 ) [6] => stdClass Object ( [id] => 8 [product_id] => 49 [price] => 14000000.0000 [created_at] => 1593019554 ))現在，為了在表中顯示數據，我使用foreach如下方法列出了價格： <?php foreach($product_prices_list as $product_price_list):?> <tr> <td><?= esc($product_price_list->created_at);?></td> <td class="text-center"><?= esc(number_format($product_price_list->price));?></td> <td class="text-center"></td> //show difference between of two price </tr> <?php endforeach;?>我可以在表中看到真實的輸出，但我需要在第三列中顯示兩個價格之間的差異，如下圖所示：我如何顯示列表中兩個價格之間的差異？！
2 回答
ITMISS
TA貢獻1871條經驗 獲得超8個贊
您只需將當前價格屬性與數組中前一個對象的價格進行比較？
像這樣的東西應該有效：
<?php foreach($product_prices_list as $key => $product_price_list):?>
<tr>
<td><?= esc($product_price_list->created_at);?></td>
<td class="text-center"><?= esc(number_format($product_price_list->price));?></td>
<td class="text-center"><?= (!empty($product_prices_list[$key - 1])) ? $product_prices_list[$key + 1]->price - $product_price_list->price: 0; ?></td> //show difference between of two price
</tr>
<?php endforeach;?>
慕田峪4524236
TA貢獻1875條經驗 獲得超5個贊
如果您運行的是 MySQL 8.0，則可以使用窗口函數直接在數據庫中計算此信息：
select
t.*,
price
- lag(price, 1, price) over(partition by product_id order by created_at)
as price_diff
from mytable t
這會向結果集中再添加一列，其中包含同一產品的當前價格與之前價格之間的差異。
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