PHP: bcmod - Manual

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

bcmod — Get modulus of an arbitrary precision number

Description

Parameters

num1: The left operand, as a string.
num2: The right operand, as a string.
scale: This parameter is used to set the number of digits after the decimal place in the result. If null, it will default to the default scale set with bcscale(), or fallback to the value of the bcmath.scale INI directive.

Return Values

Returns the modulus as a string.

Errors/Exceptions

This function throws a ValueError in the following cases:

num1 or num2 is not a well-formed BCMath numeric string.
scale is outside the valid range.

This function throws a DivisionByZeroError exception if num2 is 0.

Changelog

Version	Description
8.0.0	`scale` is now nullable.
8.0.0	Dividing by `0` now throws a DivisionByZeroError exception instead of returning null.
7.2.0	`num1` and `num2` are no longer truncated to integer, so now the behavior of bcmod() follows fmod() rather than the `%` operator.
7.2.0	The `scale` parameter was added.

Examples

Example #1 bcmod() example

<?php
bcscale(0);
echo bcmod( '5',  '3'); //  2
echo bcmod( '5', '-3'); //  2
echo bcmod('-5',  '3'); // -2
echo bcmod('-5', '-3'); // -2
?>

Example #2 bcmod() with decimals

<?php
bcscale(1);
echo bcmod('5.7', '1.3'); // 0.5 as of PHP 7.2.0; 0 previously
?>

Found A Problem?

lauris at night dot lt ¶

22 years ago

<?php
/**
 * my_bcmod - get modulus (substitute for bcmod)
 * string my_bcmod ( string left_operand, int modulus )
 * left_operand can be really big, but be carefull with modulus :(
 * by Andrius Baranauskas and Laurynas Butkus :) Vilnius, Lithuania
 **/
function my_bcmod( $x, $y )
{
    // how many numbers to take at once? carefull not to exceed (int)
    $take = 5;     
    $mod = '';

    do
    {
        $a = (int)$mod.substr( $x, 0, $take );
        $x = substr( $x, $take );
        $mod = $a % $y;    
    } 
    while ( strlen($x) );

    return (int)$mod;
}

// example
echo my_bcmod( "7044060001970316212900", 150 );
?>

drahoszdenek at gmail dot com ¶

13 years ago

The modulus can be only integer. For "floats" bcmod returns 0:

<?php
echo bcmod('10', '2.1'); // 0
?>

For real modulus you can use BN-PHP project (hosted at Bitbucket):

<?php
$eval = new \BN\Expression\ExpressionEvaluator();
$operators = new \BN\Expression\OperatorsFactory();
$eval->setOperators($operators->getOperators(array('%')));
        
echo $eval->evaluate('10 % 2.1'); // 1.6
echo $eval->evaluate('10 % -2.1'); // 1.6
echo $eval->evaluate('-10 % 2.1'); // -1.6
echo $eval->evaluate('-10 % -2.1'); // -1.6
?>