doucan2102
2010-11-09 01:31 阅读 176
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PHP foreach循环,比较两个值

I'm building a simple weight log, where there'a table that display the user's progress. I'm using Codeigniter.

    <?php foreach($logs as $log) : ?>
        <tr>
        <td><?php echo $log->date ;?></td>
        <td><?php echo $log->weight ;?> kg.</td>
        <td><!-- variation between this record and previous record. weigth[a] - weight[b] --></td>
        <td></td>
        <td><?php echo anchor('logs/edit/'.$log->id, 'Editar'); ?> <?php echo anchor('logs/delete/'.$log->id, 'Delete'); ?></td>
        </tr>
    <?php endforeach ;?>

I'm trying to calculate the variation between the first row and the second row, so as to get the weight loss or gain between logs. I was wondering how to access the loop's previous record so as to substract it from the current record's weight.

---------------------------------------
  DATE     |   WEIGHT  |   VARIATION
---------------------------------------
  Nov 20   |    70 kg  |     -1 kg      << LAST LOGGED WEIGHT, FIRST IN ARRAY
.......................................
  Nov 15   |    71 kg  |      -
---------------------------------------
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2条回答 默认 最新

  • 已采纳
    doutang6819 doutang6819 2010-11-09 01:43

    One simple way to do it:

    <?php $previousWeight = null; ?>
    <?php foreach($logs as $log) : ?>
        <tr>
        <td>
            <?php
                if ($previousWeight) {
                    echo $previousWeight - $log->weight;
                }
                $previousWeight = $log->weight;
            ?>
        </td>
        </tr>
    <?php endforeach; ?>
    

    Or, the reverse way:

    <?php
        $current = current($logs);
        $next = next($logs);
    ?>
    <?php while ($current) : ?>
        <tr>
            <td><?php echo $current->date; ?></td>
            ...
            <td>
                <?php
                    if ($next) {
                        echo $current->weight - $next->weight;
                    }
                ?>
            </td>
        </tr>
        <?php
            $current = $next;
            $next = next($logs);
        ?>
    <?php endwhile; ?>
    

    If your array keys are guaranteed to be numeric (which they probably are), this can be simplified a lot. See @William's answer.

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  • duancuisan2503 duancuisan2503 2010-11-09 01:38

    You could try using the key => value option for foreach (here). This would give you the current index in the log, so finding the previous index would be index = ($key == 0) ? $key : ($key - 1); $old_weight = $logs[$index]; (the syntax might be a bit off, but the idea is there).

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