Description:
------------
Number of return Modular_arithmetic must be positive in general but i tryed high nubmer  like(2^30++) in Modular_arithmetic, PHP gave me negative nubmer...

example:  x=2^31, y=x%20, y = negative in PHP

Reproduce code:
---------------
<?php
$number = 31;
$pow = pow(2,$number);
$random = rand(10,50);
echo ($pow%$random);
?>

Expected result:
----------------
Negative numbers..
Like
-6
-38
-44
..
..

Actual result:
--------------
nubmer of return will be positive..