php man page for gmp_nextprime

GMP_NEXTPRIME(3)							 1							  GMP_NEXTPRIME(3)

gmp_nextprime - Find next prime number

SYNOPSIS
       GMP gmp_nextprime (int  $a)

DESCRIPTION
	Find next prime number

PARAMETERS
	      o $a
		-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
	Return the next prime number greater than $a, as a GMP number.

EXAMPLES
       Example #1

	      gmp_nextprime(3) example

	      <?php
	      $prime1 = gmp_nextprime(10); // next prime number greater than 10
	      $prime2 = gmp_nextprime(-1000); // next prime number greater than -1000

	      echo gmp_strval($prime1) . "
";
	      echo gmp_strval($prime2) . "
";
	      ?>

	      The above example will output:

	      11
	      -997

NOTES
       Note

	       This function uses a probabilistic algorithm to identify primes and chances to get a composite number are extremely small.

PHP Documentation Group 													  GMP_NEXTPRIME(3)