PHP Reference

Description

int gmp_prob_prime ( resource a [, int reps])

If this function returns 0, a is definitely not prime. If it returns 1, then a is "probably" prime. If it returns 2, then a is surely prime. Reasonable values of reps vary from 5 to 10 (default being 10); a higher value lowers the probability for a non-prime to pass as a "probable" prime.

The function uses Miller-Rabin's probabilistic test.

Example 1. gmp_prob_prime() example


<?php

// definitely not a prime

echo gmp_prob_prime("6") . "\n";



// probably a prime

echo gmp_prob_prime("1111111111111111111") . "\n";



// definitely a prime

echo gmp_prob_prime("11") . "\n";

?>

The printout of the above program will be:

0
1
2