(PHP 4 >= 4.0.4, PHP 5)
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.
可以是一个 GMP 数据 resouce，或一个可以转换为数值的字符串。
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 以上例程会输出：
<?php
$gcd = gmp_gcd("12", "21");
echo gmp_strval($gcd) . "
";
?>
3