(PHP 5, PHP 7, PHP 8)
bcpowmod — Raise an arbitrary precision number to another, reduced by a specified modulus
$num
,$exponent
,$modulus
,$scale
= null
Use the fast-exponentiation method to raise
num
to the power
exponent
with respect to the modulus
modulus
.
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 0
if
this has not been set.
Returns the result as a string, or false
if modulus
is 0
or exponent
is negative.
Version | Description |
---|---|
8.0.0 |
scale is now nullable.
|
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.
?>
Note:
Because this method uses the modulus operation, numbers which are not positive integers may give unexpected results.