Php/docs/function.mt-srand
mt_srand
(PHP 4, PHP 5, PHP 7)
mt_srand — Seeds the Mersenne Twister Random Number Generator
Description
mt_srand
([ int $seed
[, int $mode
= MT_RAND_MT19937
]] ) : void
Seeds the random number generator with
seed
or with a random value
if no seed
is given.
Note:
There is no needto seed the random number generator with srand() or mt_srand() as this is done automatically.
Parameters
seed
An arbitrary int seed value.
mode
Use one of the following constants to specify the implementation of the algorithm to use.
Constant Description MT_RAND_MT19937
Uses the fixed, correct, Mersenne Twister implementation, available as of PHP 7.1.0. MT_RAND_PHP
Uses an incorrect Mersenne Twister implementation which was used as the default up till PHP 7.1.0. This mode is available for backward compatibility.
Return Values
No value is returned.
Changelog
Version | Description |
---|---|
7.1.0 | srand() has been made an alias of mt_srand(). |
7.1.0 | mt_rand() has been updated to use the fixed, correct, version of
the Mersenne Twister algorithm. To fall back to the old behaviour, use mt_srand() with |
Examples
Example #1 mt_srand() example
<?php// seed with microsecondsfunction make_seed(){ list($usec, $sec) = explode(' ', microtime()); return $sec + $usec * 1000000;}mt_srand(make_seed());$randval = mt_rand();?>
See Also
- mt_rand() - Generate a random value via the Mersenne Twister Random Number Generator
- mt_getrandmax() - Show largest possible random value
- srand() - Seed the random number generator