BC Math 函数
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bcscale

(PHP 4, PHP 5)

bcscale — Set default scale parameter for all bc math functions

说明

bool bcscale ( int $scale )

Sets the default scale parameter for all subsequent bc math functions that do not explicitly specify a scale parameter.

参数

scale

The scale factor.

返回值

成功时返回 TRUE， 或者在失败时返回 FALSE.

范例

Example #1 bcscale() example

<?php

// default scale : 3
bcscale(3);
echo bcdiv('105', '6.55957'); // 16.007

// this is the same without bcscale()
echo bcdiv('105', '6.55957', 3); // 16.007

?>

BC Math 函数
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PHP手册 - N: Set default scale parameter for all bc math functions

用户评论:

rastislav dot bostik at bwd21 dot cz (25-Jan-2012 10:20)

Previously stated one liner trailing 0 removing using rtrim() works fine except following class of subcases:

<?php
echo rtrim('100.0000', '0.'); // 1 instead 100
echo rtrim('1230.00000000', '0.'); // 123 instead 1230
?>

What seems to be working to me is using regular expression replacement. Althought it`s probably not that fast as rtrim(), I hope it should be more reliable:

<?php
function removeFloatNumStringZeroTrailer($input) {
    $patterns = array('/[\.][0]+$/','/([\.][0-9]*[1-9])([0]*)$/');
    $replaces = array('','$1');
    return preg_replace($patterns,$replaces,$input);
}

echo removeFloatNumStringZeroTrailer('100.0000'); // says 100
echo removeFloatNumStringZeroTrailer('1230.00000000'); // says 1230
?>

dcz at phpbb-seo dot com (25-Mar-2011 03:05)

The general approach for a one liner trailing 0 removing would be :
<?php
echo rtrim('1.2500000000', '0.'); // 1.25
echo rtrim('1.00000000', '0.'); // 1
?>

Which seems totally appropriate since we are working with strings, and also is likely to be the fastest way.

Nitrogen (25-Jan-2009 05:00)

Good day,
I made a little function to remove the excess zeroes after calculations.. it makes them cleaner and more presentable.

<?php

function DecimalClean($Input) {
  $Input=explode('.',$Input,2);
  if(!isset($Input[1])) $Input[1]=0;
  for($i=(strlen($Input[1])-1);$i>0;$i--) {
    if($Input[1]{$i}=='0')
      $Input[1]=substr($Input[1],0,-1);
    else break;
  }
  return(sprintf('%s%s',$Input[0],($Input[1]!='0')?".{$Input[1]}":''));
}

BCScale(10); // allow 10 decimals
$Sum = BCDiv(10,8); // make a calculation

printf("Result #1: %s\n", $Sum);
// 1.2500000000

printf("Result #2: %s\n", DecimalClean($Sum));
// 1.25

?>

Hope this helps,
Nitrogen.

mwgamera at gmail dot com (06-Dec-2007 02:45)

These functions DO NOT round off your values. No arbitrary precision libraries do it this way. It stops calculating after reaching scale of decimal places, which mean that your value is cut off after scale number of digits, not rounded. To do the rounding use something like this:
<?php
        function bcround($number, $scale=0) {
                $fix = "5";
                for ($i=0;$i<$scale;$i++) $fix="0$fix";
                $number = bcadd($number, "0.$fix", $scale+1);
                return    bcdiv($number, "1.0",    $scale);
        }
?>

invincible at limitedintelligence dot com (08-Feb-2006 11:50)

If you don't set the default scale, be careful when you're chaining together several BC math functions - since by default, these functions will round off your values, losing accuracy very quickly:

<?php
$a = 1.234
$b = 2.345
$c = 7.890

$ab = bcmul($a,$b);           // 2
$abc = bcmul($ab,$c);

echo $abc;                 // 15
?>

... compare with the answer you get when you use more decimal places:

<?php
$a = 1.234
$b = 2.345
$c = 7.890

bcscale(15);
$ab = bcmul($a,$b);           // 2.893730
$abc = bcmul($ab,$c);

echo $abc;                 // 22.83152970
?>