PHP Manual: Multiply two arbitrary precision numbers

Description

string bcmul(string $num1, string $num2, intnull $scale = null)

Multiply num1 by num2.

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 result 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.

Changelog

Version	Description
8.0.0	`scale` is now nullable.
7.3.0	bcmul now returns numbers with the requested scale. Formerly, the returned numbers may have omitted trailing decimal zeroes.

Examples

Example #1 bcmul example

<?php
echo bcmul('1.34747474747', '35', 3); // 47.161
echo bcmul('2', '4'); // 8
?>

Notes

Note:
Prior to PHP 7.3.0, bcmul may return a result with fewer digits after the decimal point than the scale parameter would indicate. This only occurs when the result doesn't require all of the precision allowed by the scale. For example:
Example #2 bcmul scale example
<?php
echo bcmul('5', '2', 2);     // prints "10", not "10.00"
?>

bcmul