(PHP 7)
gmp_random_seed — Sets the RNG seed
seedThe seed to be set for the gmp_random(), gmp_random_bits(), and gmp_random_range() functions.
可以是一个 GMP 数据 resouce，或一个可以转换为数值的字符串。
Returns NULL on success.
Issues an E_WARNING and returns FALSE if
seed is not valid.
Example #1 gmp_random_seed() example
<?php
// set the seed
gmp_random_seed(100);
var_dump(gmp_strval(gmp_random(1)));
// set the seed to something else
gmp_random_seed(gmp_init(-100));
var_dump(gmp_strval(gmp_random_bits(10)));
// set the seed to something invalid
var_dump(gmp_random_seed('not a number'));
以上例程会输出：
string(20) "15370156633245019617" string(3) "683" Warning: gmp_random_seed(): Unable to convert variable to GMP - string is not an integer in %s on line %d bool(false)