douxie9347
2018-10-09 17:08
浏览 354
已采纳

PHP：根据foreach循环中另一个变量的变化增加变量

I have a foreach loop that prints the history of line item changes in my application. Each line item has a number, and each line item can have multiple changes.

What I want to do is display the line number alongside each change when my loop executes. $i will hold the line number.

$i = 1;
foreach($lineItem as $line) {
   echo $i; //line number
   echo $line['field_changed'];
   echo $line['change_date'];
   echo $line['change_from'];
   echo $line['change_to'];
}

The code reads from a DB table called line_item_changes with the following structure:

id  line_id  parent_id
--  -------  ---------
1   2401     521
2   2401     521
3   2401     521
4   2500     521
5   2502     521
6   2502     521

I want to increment $i every time the value in $line['line_id'] changes. So that, when the results display, they look something like this:

Line #: 1
field: notes
date: 10/9/2018
from: test
to: test2

Line #: 1
field: quantity
date: 10/1/2018
from: 4
to: 3

Line #: 2
field: need_date
date: 10/1/2018
from: 10/24/2018
to: 10/27/2018

etc.

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我有一个foreach循环，用于打印应用程序中订单项更改的历史记录。 每个订单项都有一个数字，每个订单项都可以有多处更改。

我想要做的是在循环执行时显示每个更改旁边的行号。 $ i 将保留行号。 

  $ i = 1; 
foreach（$ lineItem as $ line）{
 echo $ i;  //行号
 echo $ line ['field_changed']; 
 echo $ line ['change_date']; 
 echo $ line ['change_from']; 
 echo $ line ['change_to']; 
  } 
   
 
 
代码从名为 line_item_changes 的数据库表中读取，结构如下： 
 
 
   id line_id parent_id 
-- ------- --------- 
1 2401 521 
2 2401 521 
3 2401 521 
4 2500 521 
5 2502 521 
6 2502 521  
   
 
 
每当 $ line ['line_id'] 中的值发生变化时，我想增加 $ i   。 因此，当结果显示时，它们看起来像这样： 
 
 
  Line＃：1 
field：notes 
date：10/9/2018 
 from：test 
to  ：test2 
 
Line＃：1 
field：quantity 
date：10/1/2018 
 from：4 
to：3 
 
Line＃：2 
field：need_date 
date：10/1/2018 
from  ：10/24/2018 
to：10/27/2018 
   
 
 
等。
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2条回答 默认 最新

  • dqwd71332 2018-10-09 17:30
    已采纳

    Just store the previous line_id in a variable, and update $i if the value changes. Try the following (explanation in code comments): 

    $i = 1;
$prev_line_id = null; // initializing the previous value

foreach($lineItem as $line) {

   // if the previous line_id exists
   if (isset($prev_line_id)) {

       // if previous value does not match with the current value
       if ($prev_line_id != $line['line_id']) {

           // increment the line number
           $i++;
       }
   }

   // set the previous value
   $prev_line_id = $line['line_id'];

   echo $i; //line number
   echo $line['field_changed'];
   echo $line['change_date'];
   echo $line['change_from'];
   echo $line['change_to'];
}

    Note that you can get the changing line number directly from DB query itself. You can use window functions like Dense_Rank().

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  • duanmo6937 2018-10-09 17:40

    You have to store the last line_id of the last loop and then check it with the line_id of the next loop, if they are not equal then increment $i, when $i is incremented you set $prev_line_id to the current line_id.

    $prev_line_id = $lineItem[0]['line_id'] ?? null;
$i = 0;
foreach($lineItem  as $line)
{
    if($line['line_id'] != $prev_line_id )
    {
        $i++;
        $prev_line_id = $line['line_id'];
    }

    echo $i; //line number
    echo $line['field_changed'];
    echo $line['change_date'];
    echo $line['change_from'];
    echo $line['change_to'];
}
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