php man page for gmp_prob_prime

GMP_PROB_PRIME(3)							 1							 GMP_PROB_PRIME(3)

gmp_prob_prime - Check if number is ";probably prime"

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

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

PARAMETERS
	      o $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.

	      o $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(3) example

	      <?php
	      // definitely not a prime
	      echo gmp_prob_prime("6") . "
";

	      // probably a prime
	      echo gmp_prob_prime("1111111111111111111") . "
";

	      // definitely a prime
	      echo gmp_prob_prime("11") . "
";
	      ?>

	      The above example will output:

	      0
	      1
	      2

PHP Documentation Group 													 GMP_PROB_PRIME(3)