# gmp_prob_prime

(PHP 4 >= 4.0.4, PHP 5, PHP 7)

gmp_prob_prime — Check if number is "probably prime"

### 说明

gmp_prob_prime ( GMP `$a` [, int `$reps` = 10 ] ) : int

The function uses Miller-Rabin's probabilistic test to check if a number is a prime.

### 参数

`a`

  The number being checked as a prime.

  可以是一个 GMP 数据 resouce，或一个可以转换为数值的字符串。

`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.

  可以是一个 GMP 数据 resouce，或一个可以转换为数值的字符串。

### 返回值

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.

### 范例

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