Simulation for Monty Hall Dilemma

show.php

<?php
/*
	Suppose you're on a game show, and you're given the choice of three
	doors. Behind one door is a car, behind the others, goats. You pick
	a door, say number 1, and the host, who knows what's behind the
	doors, opens another door, say number 3, which has a goat. 
	He says to you, "Do you want to pick door number 2?" 
	Is it to your advantage to switch your choice of doors?
							Craig. F. Whitaker
							Columbia, MD 
*/


for ($i = 0;  $i <1000000 ; $i++ ){

	// make choice
	$keuze = mt_rand ( 1 , 3 );
	$prijs = mt_rand ( 1 , 3 );

	// goats
	if ($prijs == 1) $goat1 = 2;
	if ($prijs == 1) $goat2 = 3;
	if ($prijs == 2) $goat1 = 1;
	if ($prijs == 2) $goat2 = 3;
	if ($prijs == 3) $goat1 = 1;
	if ($prijs == 3) $goat2 = 2;
	
	// keuze
	if ($keuze == 1) $alt1 = 2;
	if ($keuze == 1) $alt2 = 3;
	if ($keuze == 2) $alt1 = 1;
	if ($keuze == 2) $alt2 = 3;
	if ($keuze == 3) $alt1 = 1;
	if ($keuze == 3) $alt2 = 2;
 
	//lets open some doors
	if ($keuze == $goat1) $dooropen = $goat2;
	if ($keuze == $goat2) $dooropen = $goat1;
	if (($keuze != $goat1)&&($keuze != $goat2)){
			if (1==mt_rand ( 1 , 2 )){
					$dooropen = $goat2;
					}else{
					$dooropen = $goat1;
					}
			}
	
	// See if we would win by not swapping 
	if ($keuze == $prijs) $winnormaal++ ; 

	// Ok, let's take the other door...
	if (($keuze==1)&&($dooropen==2)) $keuze = 3;
	if (($keuze==1)&&($dooropen==3)) $keuze = 2;
	if (($keuze==2)&&($dooropen==1)) $keuze = 3;
	if (($keuze==2)&&($dooropen==3)) $keuze = 1;
	if (($keuze==3)&&($dooropen==2)) $keuze = 1;
	if (($keuze==3)&&($dooropen==1)) $keuze = 2;


	// See if we would win by choosing alternative door 
	if ($keuze == $prijs) $winalt++ ; 

}
	echo "\nNormaal : $winnormaal  \nAlt keuze: $winalt";
	
?>