PHP Unconference Europe 2015

bcdiv

(PHP 4, PHP 5)

bcdivDivide two arbitrary precision numbers

Description

string bcdiv ( string $left_operand = "" , string $right_operand = "" [, int $scale = int ] )

Divides the left_operand by the right_operand.

Parameters

left_operand

The left operand, as a string.

right_operand

The right operand, as a string.

scale

This optional parameter is used to set the number of digits after the decimal place in the result. You can also set the global default scale for all functions by using bcscale().

Return Values

Returns the result of the division as a string, or NULL if right_operand is 0.

Examples

Example #1 bcdiv() example

<?php

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

?>

See Also

  • bcmul() - Multiply two arbitrary precision numbers

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User Contributed Notes 4 notes

up
3
MM
6 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;
up
2
Anonymous
4 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'

?>
up
2
Gautam
7 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
?>
up
-1
cristianDOTzuddas]NOSPAM[gmailDOTcom
9 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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