(PHP 4 >= 4.0.4, PHP 5)
gmp_prob_prime — Check if number is "probably prime"
The function uses Miller-Rabin's probabilistic test to check if a number is a prime.
The number being checked as a prime.
It can be either a GMP number resource, or a numeric string given that it is possible to convert the latter to a number.
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.
It can be either a GMP number resource, or a numeric string given that it is possible to convert the latter to a number.
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.
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";
?>
上例将输出：
0 1 2