PHP | bcpowmod() Function

The bcpowmod() function in PHP is an inbuilt function and is used to raise an arbitrary precision base number to another exponent number reduced by a specified modulus. This function accepts three arbitrary precision numbers as strings and returns the base number raised to exponent modulo under a number after scaling the result to a specified precision. 

Syntax:

string bcpowmod ( $base, $exponent, $mod, $scaleVal )

Parameters: This function accepts four parameters as shown in the above syntax and explained below:

• $base: This parameter is of string type and represents the left operand or the number which is the base in which the power will be raised. This parameter is mandatory.
• $exponent: This parameter is of string type and represents the right operand or one of the numbers which represent the exponent. This parameter is mandatory.
• $mod: This parameter is of string type and accepts an operand or a number that represents the modulus. This parameter is mandatory.
• $scaleVal: This parameter is of int type and is optional. This parameter tells the number of digits that will appear after the decimal in the result of (base^exponent)%mod. Its default value is zero.

Return Value: This function returns the ($base^$exponent) % $mod result as a string. Examples:

Input:  $base = 2, $exponent = 3 $mod = 3
Output: 2
Since the parameter $scaleVal is not specified so
no digits after decimal is appeared in the 
result after evaluating result

Input:  $base = 2, $exponent = 3, $mod = 3, $scaleVal = 2
Output: 2.00

The below programs illustrate the bcpowmod() function in PHP.

Program 1: 

php

<?php
// PHP program to illustrate bcpowmod() function

// input numbers with arbitrary precision
$base = "2";
$exponent = "3";
$mod = "3";

// calculates the base^exponent % mod
// when $scaleVal is not specified
$res = bcpowmod($base, $exponent, $mod);

echo $res;

?>

Output:

2

Program 2: 

php

<?php
// PHP program to illustrate bcpowmod() function

// input numbers with arbitrary precision
$base = "2";
$exponent = "3";
$mod = "3";

// scale value
$scaleVal = 4;

// calculates the base^exponent % mod
// when $scaleVal is specified
$res = bcpowmod($base, $exponent, $mod, $scaleVal);

echo $res;

?>

Output:

2.0000

Reference: http://php.net/manual/en/function.bcpowmod.php