Monty Hall problem

montyhall.php

<?php

function play($strategy, $games = 10) {
    $wins = 0;

    for ($x = 0; $x < $games; $x++) {
        $car = rand(0, 2);

        $choice = rand(0, 2);

        $closed = array(0, 1, 2);
        if ($car == $choice) {
            unset($closed[$choice]);
            $closed = array_values($closed);
            $closed = $closed[rand(0,1)];
        } else {
            $closed = $car;
        }

        if (
            $strategy == 'switch' ||
            ($strategy == 'random' && rand(0,1))
        ) {
            $choice = $closed;
        }

        if ($car == $choice) {
            $wins++;
        }
    }

    echo "$wins/$games ",$wins/$games, " $strategy", PHP_EOL;
}

$games = 1000000;
play('stay',   $games);
play('switch', $games);
play('random', $games);

// $ php montyhall.php 
// 333389/1000000 0.333389 stay
// 666774/1000000 0.666774 switch
// 499988/1000000 0.499988 random