Problem using Round - any ideas

[mambo-no-6]

Hi

I'm having trouble with using round to round a vat calculation. I have done separated out the lines that I believe show the problem.

I can't work out why the first sprintf produces an incorrect rounded value, yet the second sprintf produces the required results. Driving me mad - can anyone put my mind at rest and stop my hair from turning grey? I'm sure it's something simple.

The code is:

<?php
$number = 691.30;
$withvat = $number * 1.15;
$total = $number * 1.15;
$vat = $total - $number;
?>
<?=sprintf("%.2F", round($vat, 2));?><br>
<?=sprintf("%.2F", round(103.695, 2));?>

[fristi]

Hi

I'm having trouble with using round to round a vat calculation. I have done separated out the lines that I believe show the problem.

I can't work out why the first sprintf produces an incorrect rounded value, yet the second sprintf produces the required results. Driving me mad - can anyone put my mind at rest and stop my hair from turning grey? I'm sure it's something simple.

The code is:

<?php
$number = 691.30;
$withvat = $number * 1.15;
$total = $number * 1.15;
$vat = $total - $number;
?>
<?=sprintf("%.2F", round($vat, 2));?><br>
<?=sprintf("%.2F", round(103.695, 2));?>

http://en.php.net/round

check out the manual. More people have encountered this problem. As a result some of them wrote their own function. Maybe you could look into that.

[Mark Baker]

It's always better to do math with money using integer cents/pence values rather than float dollars/pounds

But why round to 2dp when you're using sprintf to format to 2dp anyway

[Jake Arkinstall]

By the way, you would be better off using:

<?php
$number = 691.3;
$vat = $number * 0.15;
$total = $number + $vat;
?>
....
<?php printf('£%.2f', $vat); ?>

[crmalibu]

Keep in mind, printf() truncates

printf('%.2f', 1.555); // 1.55
echo round(1.555, 2); // 1.6