(PHP 5, PHP 7)
bcpowmod — Raise an arbitrary precision number to another, reduced by a specified modulus
$base
, string $exponent
, string $modulus
[, int $scale
= 0
] ) : string
Use the fast-exponentiation method to raise
base
to the power
exponent
with respect to the modulus
modulus
.
base
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
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Returns the result as a string, or NULL
if modulus
is 0 or exponent
is negative.
Note:
Because this method uses the modulus operation, numbers which are not positive integers may give unexpected results.
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.
?>