bcpow() only supports exponents less than or equal to 2^31-1. Also, bcpow() does not support decimal numbers. If you have scale set to 0, then the exponent is converted to an interger; otherwise an error is generated.
--
Michael Bailey
http://www.jinxidoru.combcpow
(PHP 4, PHP 5, PHP 7, PHP 8)
bcpow — Raise an arbitrary precision number to another
Description
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
-2147483648to2147483647. 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 thebcmath.scaleINI directive.
Return Values
Returns the result as a string.
Errors/Exceptions
This function throws a ValueError in the following cases:
numorexponentis not a well-formed BCMath numeric stringexponenthas a fractional partexponentorscaleis 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
scaleparameter would indicate. This only occurs when the result doesn't require all of the precision allowed by thescale. For example:Example #2 bcpow() scale example
<?php echo bcpow('5', '2', 2); // prints "25", not "25.00" ?>
See Also
- bcpowmod() - Raise an arbitrary precision number to another, reduced by a specified modulus
- bcsqrt() - Get the square root of an arbitrary precision number
- BcMath\Number::pow() - Raises an arbitrary precision number
User Contributed Notes 3 notes
<?php
bcscale(100);
/*
* Computes the natural logarithm using a series.
* @author Thomas Oldbury.
* @license Public domain.
*/
function bcln($a, $iter = 10)
{
$result = "0.0";
for($i = 0; $i < $iter; $i++)
{
$pow = (1 + (2 * $i));
$mul = bcdiv("1.0", $pow);
$fraction = bcmul($mul, bcpow(bcsub($a, "1.0") / bcadd($a, "1.0"), $pow));
$result = bcadd($fraction, $result);
}
return bcmul("2.0", $result);
}
/*
* Computes the base2 log using baseN log.
* @note Requires above functions.
* @author Thomas Oldbury.
* @license Public domain.
*/
function bclog2($a, $iter = 10)
{
return bcdiv(bcln($a, $iter), bcln("2", $iter));
}
/*
* Computes the base10 log using baseN log.
* @note Requires above functions.
* @author Thomas Oldbury.
* @license Public domain.
*/
function bclog10($a, $iter = 10)
{
return bcdiv(bcln($a, $iter), bcln("10", $iter));
}
?>