PHP Manual: Calculate GCD

GMP gmp_gcd ( GMP $a , GMP $b )

Calculate greatest common divisor of a and b. The result is always positive even if either of, or both, input operands are negative.

a: Either a GMP number resource in PHP 5.5 and earlier, a GMP object in PHP 5.6 and later, or a numeric string provided that it is possible to convert the latter to a number.
b: Either a GMP number resource in PHP 5.5 and earlier, a GMP object in PHP 5.6 and later, or a numeric string provided that it is possible to convert the latter to a number.

A positive GMP number that divides into both a and b.

Example #1 gmp_gcd example


<?php
$gcd = gmp_gcd("12", "21");
echo gmp_strval($gcd) . "\n";
?>

The above example will output: