PHP - Manual: bcscale

2024-12-23

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bcscale

(PHP 4, PHP 5, PHP 7, PHP 8)

bcscale — 设置/获取所有 bc math 函数的默认小数点保留位数

说明

bcscale(int $scale): int

设置所有 bc math 函数在未设定情况下的小数点保留位数。

bcscale(null $scale = null): int

获取当前的小数点保留位数。

参数

scale: 小数点保留位数。

返回值

设置的时候，返回之前的小数点保留位数。否则就是返回当前的位数。

更新日志

版本	说明
8.0.0	现在 `scale` 可以为 null。
7.3.0	现在 bcscale() 不仅可以设置，还可以获取当前的小数点保留位数。用于设置的时候，现在会返回之前的位数。之前 `scale` 是强制的参数，且 bcscale() 总是返回 `true`。

范例

示例 #1 bcscale() 示例


<?php

// 默认小数点位数： 3
bcscale(3);
echo bcdiv('105', '6.55957'); // 16.007

// 不调用 bcscale() 也一样
echo bcdiv('105', '6.55957', 3); // 16.007

?>

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User Contributed Notes 8 notes

down

mwgamera at gmail dot com ¶

14 years ago


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);
        }
?>

down

sicerwork at aliyun dot com ¶

5 years ago


Executing bcsacle() will change the scale value of fpm.conf, not only the current process.

down

ravenswd at gmail dot com ¶

10 years ago


Simple, easy way to remove excess trailing zeros using rtrim:
<php>
  // $total is the result of a bcmath calculation
  if ( strpos($total, '.') !== false ):
    $total = rtrim($total, '0');
    $total = rtrim($total, '.');
  endif;
</php>

down

herslyadam at gmail dot com ¶

8 years ago


edited bcround function with negative number support:
<?php
function bcround($number, $scale=0) {
    if($scale < 0) $scale = 0;
    $sign = '';
    if(bccomp('0', $number, 64) == 1) $sign = '-';
    $increment = $sign . '0.' . str_repeat('0', $scale) . '5';
    $number = bcadd($number, $increment, $scale+1);
    return bcadd($number, '0', $scale);
}
?>

down

-1

nemesarial at gmail dot com ¶

6 years ago


To remove trailing zeros when using large bcscale number can be done by casting to float when ready to display the number.

<?php
bcscale(15);
$a=123.456;
$b=0.123;

$_ab=bcadd($a,$b);
echo $_ab;
// 123.579000000000000

$ab = (float)$_ab;
echo $ab;
// 123.579

?>

down

-2

invincible at limitedintelligence dot com ¶

16 years ago


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
?>

down

-1

yan dot uniko dot 102 at gmail dot com ¶

1 year ago


Does not work with big scale values, but accept INT as type, but can not process the max INT value, by example for calculate the cube root:

<?php

echo pow(1331, 1/3); // 11 (11^3=1331)
echo bcpow(1331, bcdiv(1, 3, PHP_INT_MAX)); // 1 ??
echo bcdiv(1, 3, PHP_INT_MAX); // 0 ??

down

-6

rastislav dot bostik at bwd21 dot cz ¶

10 years ago


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
?>

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官方地址：https://www.php.net/manual/en/function.bcscale.php

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PHP官方手册 - 互联网笔记

bcscale

说明

参数

返回值

更新日志

范例

User Contributed Notes 8 notes