PHP Manual: Raise an arbitrary precision number to another

Description

string bcpow(string $num, string $exponent, intnull $scale = null)

Raise num to the power exponent.

Parameters

num: The base, as a string.
exponent: The exponent, as a string. Must be a value with no fractional part. The valid range of the exponent is platform specific, but is at least -2147483648 to 2147483647.
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:

num or exponent is not a well-formed BCMath numeric string
exponent has a fractional part
exponent or scale is outside the valid range

This function throws a DivisionByZeroError exception if num is 0 and exponent is a negative value.

Changelog

Version	Description
8.4.0	Negative powers of `0` previously returned `0`, but now throw a DivisionByZeroError exception.
8.0.0	When `exponent` has a fractional part, it now throws a ValueError instead of truncating.
7.3.0	bcpow now returns numbers with the requested scale. Formerly, the returned numbers may have omitted trailing decimal zeroes.

Examples

Example #1 bcpow example

<?php

echo bcpow('4.2', '3', 2); // 74.08

?>

Notes

Note:
Before PHP 7.3.0 bcpow 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 bcpow scale example
<?php
echo bcpow('5', '2', 2);     // prints "25", not "25.00"
?>

bcpow