(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.
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).
scale此可選參數(shù)用于設(shè)置結(jié)果中小數(shù)點后的小數(shù)位數(shù)。也可通過使用
bcscale() 來設(shè)置全局默認的小數(shù)位數(shù)，用于所有函數(shù)。如果未設(shè)置，則默認為 0。
Returns the result as a string, or false if modulus
is 0 or exponent is negative.
| 版本 | 說明 |
|---|---|
| 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.
?>
注意:
Because this method uses the modulus operation, numbers which are not positive integers may give unexpected results.