Form Submit, keep variable?

So I set up a simple little validation on a form.
Say I create two variables each with a random number between 1 and 10.
and then on my form I show: $x + $y = [ ] and make the user enter it.
Then after the form is submitted it checks to see if $x + $y = $_POST['validation'];
The problem is that when the form is submitted $x and $y are re-randomized.
Because the page is loaded. How to I counter-act this? I don't want to put a hidden field on the form and have that submit the variable.
+rep for help, thanks a lot

 

Something like,

if(!(isset($_POST['validation']))) {
generate your random numbers
}

 

doesn't work, because the page is reloaded so then it doesn't even create the random numbers

 

You'll probably have to do it via sessions. Just see if the session variables are set and use them. If they're not, randomise and set them first.

 

Ok, I assumed you'd stored them in a session variable and were asking about the logic. Something like this then,

<?
session_start();

if((isset($_POST['number_sum'])) && (($_SESSION[x] + $_SESSION[y]) == $_POST[number_sum])){

echo "Correct!  ". $_SESSION[x] . "+" . $_SESSION[y] . "=" . $_POST['number_sum'];

}
else {
        $_SESSION[x] = rand(0,10) + 1;
        $_SESSION[y] = rand(0,10) + 1;
?>
<form method=POST action='<? echo $_SERVER[PHP_SELF];?>'>
<? echo $_SESSION[x]; ?> +
<? echo $_SESSION[y]; ?> = <input type=text size=2 name=number_sum>
<input type=submit value=Submit>
</form>
<? } ?>

Code (markup):

 

I got it working with some stealing a little of your code, thanks +rep for both of you