random contest winner

doobster

Hello,

I am wanting to make something along the following lines:

Everytime a member visits a page I want to determine if they are a winner of a random contest.

I want to determine a winner with odds.

For example a winner may win something with odds of 1 in 5000. So each time the page is loaded it will randomly check if they win.

Now after that part is done I want to take it one step further.

I want to run multiple contests on the same page with different odds. Of course I only want a person to be able to win one of the different contests at any one time.

So one contest can be to win $5 with odds of 1 in 10000. Next contest can be to win $3 with odds of 1 in 5000. Next contest can win $1 with odds of 1 in 1000, etc.....

Does someone already have something like this that they can share or can someone provide me with a some starter code that I can expand on.

The thing I am having the most trouble with is doing the odds.

Weedpacket

Well, [man]rand[/man] (better: [man]mt_rand[/man]) will generate pseudorandom numbers for you. You can ask for mt_rand(0,4999), and then see if it's <1 for 1 in 5000, <2 for 2 in 5000, etc.

As for how to calculate odds, this might help.

doobster

ok so using the rand. would something like this work?


srand((double)microtime()*1000000);
$randnum = rand(0, 10000);

switch($randnum) {

   case 1:                 // 1 in 10000 odds
        echo("You win $5.");
        break;
   case 2:                 // 2 in 10000 odds
        echo("You win $3.");
        break;
   case 3:                 // 3 in 10000 odds
        echo("You win $1.");
        break;
    default:                 // not a winner
        echo("You did not win");
        break;

}

now I know the rand() is not truley random. so is there a better way or will the above do the trick?

Weedpacket

No, because the odds of "2" being drawn is the same as the odds of "1" being drawn. That's why I said "<1" and "<2"; because there's only one number in the range [0,4999] that is less than 1, two numbers in the range [0,4999] that are less than 2... and 5000 numbers in the range [0,4999] that are less than 5000.

Like I pointed out, [man]mt_rand[/man] is more reliable. Certainly it's random enough for your purposes.

doobster

Oh whoops I missed that error in my code with the <.

So if I switched it to:

$randnum = mt_rand(0, 10000); 

switch($randnum) { 

   case <1:                 // 1 in 10000 odds 
        echo("You win $5."); 
        break; 
   case <2:                 // 2 in 10000 odds 
        echo("You win $3."); 
        break; 
   case <3:                 // 3 in 10000 odds 
        echo("You win $1."); 
        break; 
    default:                 // not a winner 
        echo("You did not win"); 
        break; 

}

that should do the trick?