gmp_invert

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

gmp_invert — Inverse by modulo

说明

Computes the inverse of num1 modulo num2.

参数

num1: GMP 对象或 int ，或数字string。
num2: GMP 对象或 int ，或数字string。

返回值

A GMP number on success or false if an inverse does not exist.

范例

Example #1 gmp_invert() example


<?php
echo gmp_invert("5", "10"); // no inverse, outputs nothing, result is FALSE
$invert = gmp_invert("5", "11");
echo gmp_strval($invert) . "\n";
?>

以上例程会输出：

User Contributed Notes

athamidn at gmail dot com 06-Apr-2020 11:31


Example #2 gmp_invert() example

<?php

echo gmp_invert("5", "10"); // no inverse, outputs nothing, result is FALSE



It means (5 * x ) mod 10 = 1. And with this function we want a value for x, because of mod 10, x should be {1.. 10-1(9)}, so :



5 * 1 mod 10 = 5 

5 * 2 mod 10 = 0

5 * 3 mod 10 = 5

5 * 4 mod 10 =  0

5 * 5 mod 10 = 5

5 * 6 mod 10 = 0

5 * 7 mod 10 = 5

5 * 8 mod 10 = 0

5 * 9 mod 10 = 5

We don't have any 1 in the results. so it will be False.



$invert = gmp_invert("5", "11");



echo gmp_strval($invert) . "\n";

?>



The above example will output:



9



5 * 9 mod 11 = 1