bcpowmod

PHP Manual
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Description

string bcpowmod ( string x, string y, string modulus [, int scale])

Use the fast-exponentiation method to raise x to the power y with respect to the modulus modulus. The optional scale can be used to set the number of digits after the decimal place in the result.

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: Because this method uses the modulus operation, non-natural numbers may give unexpected results. A natural number is any positive non-zero integer.