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PHP Sum Array - sum only elemants of an array

Answer 1

+7 A:

I imagine you could use a combination of array_sum and array_slice:

$arr = array(1, 2, 3, 4);
echo "First sum: " . array_sum(array_slice($arr,0,2));
echo '<br />';
echo "Second sum: " . array_sum(array_slice($arr,2,3));

Output:

First sum: 3
Second sum: 7

EDIT: based on the updated question, you would need something like:

$str = "55% 23% 12% 20%";

// the below line can be omitted because of the way PHP handles conversions
$str = str_replace('%', '', $str);
$arr = split(' ', $str);
echo "First sum: " . array_sum(array_slice($arr,0,2)) . '%';
echo '<br />';
echo "Second sum: " . array_sum(array_slice($arr,2,3)) . '%';

Output:

First sum: 78%
Second sum: 32%

karim79 2010-04-21 09:38:50

I can't quite seem to get this work - I think the reason is I am working on a particular part of the array $row[6] - the above example is using the whole array $arr?Unless I'm not understanding something correctly, which is very very likely!

Homer_J 2010-04-21 10:23:27

@Homer_J - the above was intended as a self-contained working example. Just change `$arr` to `$row[6]` and it should be fine.

karim79 2010-04-21 11:52:58

@karim79 - thanks for the note - I had tried with replacing $arr with $row[6] but it simply doesn't bring anything back, just blank.

Homer_J 2010-04-21 12:16:37

@Homer_J - updated my answer.

karim79 2010-04-21 12:51:42

@karim - thanks again for taking the time to reply but that doesn't work either - as I have more than just four figures stored in the array - hence that fact that I'm using $row[6] to get the fours figures from the array - but there is other stuff there as well.

Homer_J 2010-04-21 13:20:51

Answer 2

+1 A:

Based on the assumption that you always want to sum every two rows, you could do it as follows:

// This for-loop is intended as a replacement for your 
// innermost while-loop (rows 6-14 in your question).
// I used a for-construct because we need to count the 
// cycles, and it will do it for us.
// The condition for terminating the loop is still the same
// as in the original while-loop.

?><tr><?php
for ($rownum = 1; $row = $result->fetch_row(); $rownum++) {
    if ($rownum == 1) {
        ?>
        <td class='qnum'><span class='bold'><?php echo $row[3] ?></span></td>
        <td class='qtext'><?php echo $row[4] ?> (<span class='italics'><?php echo $row[5] ?></span>)</td><td></td>
        <?php
    }

    // Sum and display on even cycles 
    // as <N> modulo 2 == 0 is true only on even numbers
    if ($rownum % 2 == 0) {
        // Display the formatted value,
        // at the same time adding the previous cycles value to this one
        ?><td class='set1'><?php echo number_format($tmp + $row[6], 0) ?>%</td><?php

    // Store the value of $row[6] on odd cycles
    } else {
        $tmp = $row[6];
    }
}
?></tr><?php

nikc 2010-04-21 12:56:02

@nikc - thanks for taking the time but I'm not sure how the above would fit with my existing code - can't make sense of it I'm afraid. Looking at it it isn't going to give me what I need.

Homer_J 2010-04-21 13:22:14

@Homer: it is intended as a replacement for your innermost `while` loop. I added some comments to (hopefully) clarify my meaning.

nikc 2010-04-21 14:39:24

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PHP Sum Array - sum only elemants of an array

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