bcscale()

(PHP 4, PHP 5, PHP 7)

设置所有bc数学函数的默认小数点保留位数

说明

bcscale(int $scale): bool

设置所有bc数学函数的未设定情况下得小数点保留位数.

参数

$scale

小数点保留位数.

返回值

成功时返回TRUE，或者在失败时返回FALSE。

范例

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
?>

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);
    }
?>

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

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);
}
?>

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>

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
?>

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
?>

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
?>