PHP 8.1.24 Released!

# gmp_nextprime

(PHP 5 >= 5.2.0, PHP 7, PHP 8)

gmp_nextprimeFind next prime number

### Description

gmp_nextprime(GMP|int|string `\$num`): GMP

Find next prime number

### Parameters

`num`

A GMP object, an int or a numeric string.

### Return Values

Return the next prime number greater than `num`, as a GMP number.

### Examples

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 -1000echo gmp_strval(\$prime1) . "\n";echo gmp_strval(\$prime2) . "\n";?>`

The above example will output:

```11
2
```

### Notes

Note:

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

`Negative numbers N always have at least four factors: N*1=N and abs(N)*-1=N. Therefore, even if "natural number" weren't in the definition of a prime (which it is), no negative number would ever qualify. Therefore, the next-largest prime number to any negative number is always 2.`
`Prime numbers are positive, non-zero numbers that have exactly two factors. No more, no less. So testing negative numbers doesn't really make any sense.`
`It seems gmp_nextprime on negative numbers always returns 2.` 