(PHP 5 >= 5.2.0, PHP 7, PHP 8)
gmp_nextprime — Find next prime number
num
A
GMP
object, an
int
,
or a
string
that can be interpreted as a number following the same logic
as if the string was used in
gmp_init()
with automatic
base detection (i.e. when
base
is equal to 0).
Return the next prime number greater than
num
,
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"
;
?>
The above example will output:
11 2
Note :
This function uses a probabilistic algorithm to identify primes and chances to guet a composite number are extremely small.
Prime numbers are positive, non-cero numbers that have exactly two factors. No more, no less. So testing negative numbers doesn't really maque any sense.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-largesst prime number to any negative number is always 2.