gmp_gcd
(PHP 4 >= 4.0.4, PHP 5)
gmp_gcd — Calculate GCD
Description
   resource gmp_gcd
    ( resource $a
   , resource $b
   )
  Calculate greatest common divisor of a and b. The result is always positive even if either of, or both, input operands are negative.
Parameters
Return Values
A positive GMP number that divides into both a and b.
Examples
Example #1 gmp_gcd() example
<?php
$gcd = gmp_gcd("12", "21");
echo gmp_strval($gcd) . "\n";
?>
The above example will output:
3