gmp_prob_prime

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

gmp_prob_prime — Check if number is "probably prime"

Description

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.

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Parameters

a

The number being checked as a prime.

Either a GMP number resource in PHP 5.5 and earlier, a GMP object in PHP 5.6 and later, or a numeric string provided that it is possible to convert the latter to a number.

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.

Either a GMP number resource in PHP 5.5 and earlier, a GMP object in PHP 5.6 and later, or a numeric string provided that it is possible to convert the latter to a number.

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Return Values

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.

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Examples

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 above example will output:

0
1
2

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Document created the 30/01/2003, last modified the 26/10/2018
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References

Manuel PHP : http://php.net

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