Marsaglia polar method in PHP - stats_rand_gen_normal polyfill

stats_rand_gen_normal.php

<?php
if (!function_exists('stats_rand_gen_normal')) {
    function stats_rand_gen_normal($mu, $sigma) {
        do {
            $u = (rand() / getrandmax()) * 2 - 1;
            $v = (rand() / getrandmax()) * 2 - 1;
            $s = $u * $u + $v * $v;
        } while ($s >= 1 || $s == 0);

        $multiplier = sqrt(-2 * log($s) / $s);

        return $mu + $sigma * $u * $multiplier;
    }
}