bcpowmod
(PHP 5, PHP 7, PHP 8)
bcpowmod — Raise an arbitrary precision number to another, reduced by a specified modulus
Description
string
$num,string
$exponent,string
$modulus,?int
$scale = null): string
Use the fast-exponentiation method to raise
num to the power
exponent with respect to the modulus
modulus.
Parameters
-
num -
The base, as an integral string (i.e. the scale has to be zero).
-
exponent -
The exponent, as an non-negative, integral string (i.e. the scale has to be zero).
-
modulus -
The modulus, as an integral string (i.e. the scale has to be zero).
-
scale -
This optional parameter is used to set the number of digits after the decimal place in the result. If omitted, it will default to the scale set globally with the bcscale() function, or fallback to
0if this has not been set.
Return Values
Returns the result as a string, or false if modulus
is 0 or exponent is negative.
Changelog
| Version | Description |
|---|---|
| 8.0.0 |
scale is now nullable.
|
Examples
The following two statements are functionally identical. The bcpowmod() version however, executes in less time and can accept larger parameters.
<?php
$a = bcpowmod($x, $y, $mod);
$b = bcmod(bcpow($x, $y), $mod);
// $a and $b are equal to each other.
?>
Notes
Note:
Because this method uses the modulus operation, numbers which are not positive integers may give unexpected results.
