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bcdiv

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

bcdiv — 两个任意精度的数字除法计算

说明

bcdiv(string $num1, string $num2, ?int $scale = null): string

num1 除以 num2。

参数

num1: 被除数，字符串类型。
num2: 除数，字符串类型。
scale: 此可选参数用于设置结果中小数点后的小数位数。也可通过使用 bcscale() 来设置全局默认的小数位数，用于所有函数。如果未设置，则默认为 0。

返回值

返回字符串类型的结果。如果 num2 是 0 结果为 null。

更新日志

版本	说明
8.0.0	现在 `scale` 可以为 null。

示例

示例 #1 bcdiv() 示例

<?php

echo bcdiv('105', '6.55957', 3);  // 16.007

?>

参见

bcmul() - 两个任意精度数字乘法计算

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User Contributed Notes 4 notes

down

MM ¶

15 years ago

Perhaps some one can find useful this function to compute the modular inverse of a integer (extended euclidean algorithm):

  function invmod($a,$b) {
    $n=$b;
    $x=0; $lx=1; $y=1; $ly=0;
    while ($b) {
      $t=$b;
      $q=bcdiv($a,$b,0);
      $b=bcmod($a,$b);
      $a=$t;
      $t=$x; $x=bcsub($lx,bcmod(bcmul($q,$x),$n)); $lx=$t;
      $t=$y; $y=bcsub($ly,bcmod(bcmul($q,$y),$n)); $ly=$t;
    }
    if (bccomp($lx,0) == -1)
      $lx=bcadd($lx,$n);
    return $lx;
  }

  // verify

  $n="2447995268898324993537772139997802321";
  $t="64941057316178801556773346239351236811";
  $m="123456789";
  $i=invmod($t,$n);
  // (t*m)*inv(t) is m
  echo bcmod(bcmul(bcmod(bcmul($t,$m),$n),$i),$n) == $m;

down

-2

Anonymous ¶

13 years ago

The custom bcdiv function listed at the top of this page produces very different results from bcdiv, as it rounds instead of truncating the result. Consider the following:

<?php

function bcdiv_cust( $first, $second, $scale = 0 )
{
    $res = $first / $second;
    return round( $res, $scale );
}

echo bcdiv('1','2','0') . " vs. " bcdiv_cust('1','2','0');  // prints '0 vs. 1'

?>

down

-7

Gautam ¶

16 years ago

<?php
 //converting in to required precision of decimal points
$result= bcdiv(89.99999999997,2.57865741235478,2);
 echo "$result";  // 34.90 result with 2 decimal points
?>

down

-10

cristianDOTzuddas]NOSPAM[gmailDOTcom ¶

18 years ago

Decimal to binary conversion, using BC Math.
Note: this function is VERY slow if the decimal number is too big!

<?
function bc_decbin($dec_str) {
    if (strlen($dec_str)>0) {
        $bin_str = '';
        do {
            if (((int)$dec_str[strlen($dec_str)-1] % 2) === 0)
                $bin_str .= '0';
            else
                $bin_str .= '1';
            
            $dec_str = bcdiv($dec_str, '2');
        } while ($dec_str!='0');
        
        return strrev($bin_str);
    }
    else
        return null;
}
?>

-----
Cristian
www.CodeFlower.com

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