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PHP Manual

# srand

(PHP 4, PHP 5)

srand — Seed the random number generator

### Description

void srand ([ int `$seed` ] )

Seeds the random number generator with `seed` or with a random value if no `seed` is given.

> Note: As of PHP 4.2.0, there is no need to seed the random number generator with srand() or mt_srand() as this is now done automatically.

### Parameters

`seed`

  Optional seed value

### ChangeLog

Version | Description
--- | ---
Since 4.2.0 | The `seed` becomes optional and defaults to a random value if omitted.

### Examples

Example#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();
?>`

### See Also

- rand()
- getrandmax()
- mt_srand()

sqrt
tan
Math Functions
PHP Manual