Picking random element by user defined weights [duplicate]

Answer 1

Here is a simple implementation:

function Probability($data, $number = 1)
{
    $result = array();

    if (is_array($data) === true)
    {
        $data = array_map('abs', $data);
        $number = min(max(1, abs($number)), count($data));

        while ($number-- > 0)
        {
            $chance = 0;
            $probability = mt_rand(1, array_sum($data));

            foreach ($data as $key => $value)
            {
                $chance += $value;

                if ($chance >= $probability)
                {
                    $result[] = $key; unset($data[$key]); break;
                }
            }
        }
    }

    return $result;
}

With this function you can specify how many unique weighted random elements you want (IDEOne).