Seeds the random number generator with seed.
| // seed with microseconds
function make_seed() {
    list($usec, $sec) = explode(' ', microtime());
    return (float) $sec + ((float) $usec * 100000);
}
mt_srand(make_seed());
$randval = mt_rand(); | 
See also mt_rand(), mt_getrandmax(), srand(), rand(), and getrandmax().