bcpowmod
(PHP 5, PHP 7, PHP 8)
bcpowmod — Raise an arbitrary precision number to another, reduced by a specified modulus
說明
string
$num,string
$exponent,string
$modulus,?int
$scale = null): string
Use the fast-exponentiation method to raise
num to the power
exponent with respect to the modulus
modulus.
參數
-
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 -
此可選參數用於設定結果中小數點后的小數位數。也可通過使用 bcscale() 來設定全域性預設的小數位數，用於所有函式。如果未設定，則預設為
0。
返回值
Returns the result as a string, or false if modulus
is 0 or exponent is negative.
更新日誌
| 版本 | 說明 |
|---|---|
| 8.0.0 |
scale is now nullable.
|
範例
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.
?>
註釋
注意:
Because this method uses the modulus operation, numbers which are not positive integers may give unexpected results.