Lottery: simulates unfair/weighted die rolls

Lottery.php

/**
 * Beware: Returns a winner even if the collective drop chance is below 100%.
 * If that behavior is undesired, add some logic in getWinner to prevent it.
 */

    class Lottery {
        /**
         * list of entries in the lottery. Elements are of the form
         * array('participant' => (mixed),
         *       'lots' => (float)),
         */
        private $_entries = array();
    
        /**
         * total number of lots in the pool
         * Lots can come in decimals as well, like 0.02
         * @var float
         */
        private $_lotsTotal = 0;
    
        /**
         * Adds a new entry to the lottery, 
         * i.e. a participant with a given number of lots
         * @param mixed $participant
         * @param float $lots
         */
        public function addEntry($participant, $lots = 1) {
            $this->_entries[] = array(
                'participant' => $participant,
                'lots' => $lots,
            );
            $this->_lotsTotal += $lots;
        }
    
        /**
         * Determines the winner of the lottery based on the number of lots that
         * each participant has. Lots and their owners are all lined up, then
         * the RNG determines the position of the winning lot.
         * @return mixed
         */
        public function getWinner() {
            if($this->_lotsTotal == 0) { return false; }

            // * 1,000,000, to make sure that lots in decimal form are handled correctly
            $rand = mt_rand(0, $this->_lotsTotal * 1000000);

            $currentLot = 0;
            foreach($this->_entries as  as $entry) {
                $currentLot += $entry['lots'] * 1000000;
                if($currentLot >= $rand) {
                    return $entry['participant'];
                }
            }
            return false; // should never happen
        }
    }