bcpowmod

(PHP 5, PHP 7)

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

string bcpowmod ( string $left_operand, string $right_operand, string $modulus [, int $scale = 0 ] )

Use the fast-exponentiation method to raise left_operand to the power right_operand with respect to the modulus modulus.

Parameters:

left_operand

The left operand, as a string.

right_operand

The right operand, as a string.

modulus

The modulus, as a string.

scale

This 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:

Returns the result as a string, or NULL if modulus is 0.

Notes:

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

Examples:

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.

?>