PHP 7.2.0 Release Candidate 4 Released

# gmp_nextprime

(PHP 5 >= 5.2.0)

gmp_nextprimeFind next prime number

### Description

resource gmp_nextprime ( int \$a )

Find next prime number

### Parameters

a

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 Values

Return the next prime number greater than a, 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
-997
```

### Notes

Note:

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

add a note

### User Contributed Notes 3 notes

Anonymous
1 year ago
``` It seems gmp_nextprime on negative numbers always returns 2. ```
IceMetalPunk at gmail dot com
8 months ago
``` 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. ```
Tommy Lynge Jrgensen
1 year ago
``` 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. ```