(PHP 5 >= 5.2.0)
gmp_nextprime — Find next prime number
Find next prime number
It can be either a GMP number resource, or a numeric string given that it is possible to convert the latter to a number.
Return the next prime number greater than a , as a GMP number.
Example#1 gmp_nextprime() 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) . "\n";
echo gmp_strval($prime2) . "\n";
?>
Результат выполнения данного примера:
11
-997
Note: This function uses a probabilistic algorithm to identify primes and chances to get a composite number are extremely small.