gmp_prob_prime
gmp_prob_prime
(PHP 4 >= 4.0.4, PHP 5, PHP 7)
gmp_prob_prime — Check if number is "probably prime"
Description
int gmp_prob_prime ( GMP $a [, int $reps = 10 ] )
The function uses Miller-Rabin's probabilistic test to check if a number is a prime.
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.
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.
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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https://secure.php.net/manual/en/function.gmp-prob-prime.php