Weighted random function

weight_rand.php

<?php

/**
* @param array $data array of "key => weight" data to get random key from, all weights must be positive integers
* @return mixed key from $data array choosen by weighted random
*/
function weightRandom(array $data)
{
    $c = count($data);
    if (!$c) {
        return false;
    } elseif ($c == 1) {
        return key($data);
    }

    $weight = rand(1, array_sum($data));

    foreach ($data as $k => $w) {
        $weight -= $w;
        if ($weight <= 0) {
            return $k;
        }
    }
};