(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.
baseThe 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).
scaleThis 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.
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.
?>