srand

(PHP 3, PHP 4 , PHP 5)

srand -- Seed the random number generator

Description

void srand ( [int seed])

Seeds the random number generator with seed. Since PHP 4.2.0, the seed becomes optional and defaults to a random value if omitted.

範例 1. srand() example

<?php
// seed with microseconds
function make_seed()
{
    list(
$usec, $sec) = explode(' ', microtime());
    return (float)
$sec + ((float) $usec * 100000);
}
srand(make_seed());
$randval = rand();
?>

注: 由PHP 4.2.0 始,您不需要再使用 srand()mt_srand() 為亂數產生器提供種子,因為這已自動的提供了。

See also: rand(), getrandmax(), and mt_srand().