bcpowmod

(PHP 5, PHP 7, PHP 8)

bcpowmodRaise an arbitrary precision number to another, reduced by a specified modulus

说明

bcpowmod ( string $num , string $exponent , string $modulus , int|null $scale = null ) : string

Use the fast-exponentiation method to raise num to the power exponent with respect to the modulus modulus.

参数

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

此可选参数用于设置结果中小数点后的小数位数。也可通过使用 bcscale() 来设置全局默认的小数位数,用于所有函数。如果未设置,则默认为 0

返回值

Returns the result as a string, or false if modulus is 0 or exponent is negative.

注释

注意:

Because this method uses the modulus operation, numbers which are not positive integers may give unexpected results.

更新日志

版本 说明
8.0.0 scale is now nullable.

范例

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.

?>

参见

  • bcpow() - 任意精度数字的乘方
  • bcmod() - 任意精度数字取模