(PHP 4 >= 4.0.4, PHP 5, PHP 7)
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.
aThe number being checked as a prime.
PHP 5.5 之前为 GMP 数值资源，PHP 5.6 之后为 GMP 对象或数字，或可以转为数字的字符串。
reps
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.
PHP 5.5 之前为 GMP 数值资源，PHP 5.6 之后为 GMP 对象或数字，或可以转为数字的字符串。
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";
?>
以上例程会输出：
0 1 2