(PHP 4, PHP 5)
mt_srand — 播下一个更好的随机数发生器种子
$seed
)
用
seed 来给随机数发生器播种。从 PHP 4.2.0
版开始，seed 参数变为可选项，当该项为空时，会被设为随时数。
Example #1 mt_srand() 范例
<?php
// seed with microseconds
function make_seed()
{
list($usec, $sec) = explode(' ', microtime());
return (float) $sec + ((float) $usec * 100000);
}
mt_srand(make_seed());
$randval = mt_rand();
?>
Note: 自 PHP 4.2.0 起，不再需要用 srand() 或 mt_srand() 给随机数发生器播种 ，因为现在是由系统自动完成的。
参见 mt_rand()， mt_getrandmax() 和 srand()。
seed
An optional seed value
没有返回值。
| 版本 | 说明 |
|---|---|
| Since 4.2.0 |
The seed becomes optional
and defaults to a random value if omitted.
|
| Since 5.2.1 | The Mersenne Twister implementation in PHP now uses a new seeding algorithm by Richard Wagner. Identical seeds no longer produce the same sequence of values they did in previous versions. This behavior is not expected to change again, but it is considered unsafe to rely upon it nonetheless. |
Example #2 mt_srand() example
<?php
// seed with microseconds
function make_seed()
{
list($usec, $sec) = explode(' ', microtime());
return (float) $sec + ((float) $usec * 100000);
}
mt_srand(make_seed());
$randval = mt_rand();
?>