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);
}
?>
PHP - Manual: bcscale
2024-04-27
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
?>
add a note
User Contributed Notes 8 notes
mwgamera at gmail dot com ¶
14 years ago
sicerwork at aliyun dot com ¶
5 years ago
Executing bcsacle() will change the scale value of fpm.conf, not only the current process.
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>
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);
}
?>
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
?>
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 $abc; // 22.83152970
?>
yan dot uniko dot 102 at gmail dot com ¶
1 year ago
Does not work with big scale values, but accept INT as type, but can not process the max INT value, by example for calculate the cube root:
<?php
echo pow(1331, 1/3); // 11 (11^3=1331)
echo bcpow(1331, bcdiv(1, 3, PHP_INT_MAX)); // 1 ??
echo bcdiv(1, 3, PHP_INT_MAX); // 0 ??
rastislav dot bostik at bwd21 dot cz ¶
10 years ago
Previously stated one liner trailing 0 removing using rtrim() works fine except following class of subcases:
<?php
echo rtrim('100.0000', '0.'); // 1 instead 100
echo rtrim('1230.00000000', '0.'); // 123 instead 1230
?>
What seems to be working to me is using regular expression replacement. Althought it`s probably not that fast as rtrim(), I hope it should be more reliable:
<?php
function removeFloatNumStringZeroTrailer($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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