bcpowmod
(PHP 5, PHP 7, PHP 8)
Raise an arbitrary precision number to another, reduced by a specified modulus
Description
Use the fast-exponentiation method to raise num to the power exponent with respect to the modulus modulus.
Parameters
numThe base, as an integral string (i.e. the scale has to be zero).
exponentThe exponent, as an non-negative, integral string (i.e. the scale has to be zero).
modulusThe modulus, as an integral string (i.e. the scale has to be zero).
Return Values
Returns the result as a string.
Errors/Exceptions
This function throws a ValueError in the following cases:
num,exponentormodulusis not a well-formed BCMath numeric stringnum,exponentormodulushas a fractional partexponentis a negative valuescaleis outside the valid range
This function throws a DivisionByZeroError exception if modulus is 0.
Changelog
| Version | Description |
|---|---|
| 8.0.0 | scale is now nullable. |
| 8.0.0 | Now throws a ValueError instead of returning false if exponent is a negative value. |
| 8.0.0 | Dividing by 0 now throws a DivisionByZeroError exception instead of returning false. |
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
Because this method uses the modulus operation, numbers which are not positive integers may give unexpected results.