(PHP 4 >= 4.0.4, PHP 5, PHP 7)
gmp_gcd — Calculate GCD
Calculate greatest common divisor of a and
b. The result is always positive even if
either of, or both, input operands are negative.
a可以是一个 GMP 数据 resouce，或一个可以转换为数值的字符串。
b可以是一个 GMP 数据 resouce，或一个可以转换为数值的字符串。
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";
?>
以上例程会输出：
3