If you need a predictable set of numbers for a given seed, you may use the following Pure-PHP implementation of a Mersenne Twister
<?php
class Mersenne_Twister
{
private $state = array ();
private $index = 0;
public function __construct($seed = null) {
if ($seed === null)
$seed = mt_rand();
$this->setSeed($seed);
}
public function setSeed($seed) {
$this->state[0] = $seed & 0xffffffff;
for ($i = 1; $i < 624; $i++) {
$this->state[$i] = (((0x6c078965 * ($this->state[$i - 1] ^ ($this->state[$i - 1] >> 30))) + $i)) & 0xffffffff;
}
$this->index = 0;
}
private function generateTwister() {
for ($i = 0; $i < 624; $i++) {
$y = (($this->state[$i] & 0x1) + ($this->state[$i] & 0x7fffffff)) & 0xffffffff;
$this->state[$i] = ($this->state[($i + 397) % 624] ^ ($y >> 1)) & 0xffffffff;
if (($y % 2) == 1) {
$this->state[$i] = ($this->state[$i] ^ 0x9908b0df) & 0xffffffff;
}
}
}
public function getNext($min = null, $max = null) {
if (($min === null && $max !== null) || ($min !== null && $max === null))
throw new Exception('Invalid arguments');
if ($this->index === 0) {
$this->generateTwister();
}
$y = $this->state[$this->index];
$y = ($y ^ ($y >> 11)) & 0xffffffff;
$y = ($y ^ (($y << 7) & 0x9d2c5680)) & 0xffffffff;
$y = ($y ^ (($y << 15) & 0xefc60000)) & 0xffffffff;
$y = ($y ^ ($y >> 18)) & 0xffffffff;
$this->index = ($this->index + 1) % 624;
if ($min === null && $max === null)
return $y;
$range = abs($max - $min);
return min($min, $max) + ($y % ($range + 1));
}
}
?>
