PHP Rand() resetting in maths game - php

Question

I'm using PHP's Rand() function to generate two random numbers that I can compare against the user's, and echo out a success message if the user's answer equals (1st random number + 2nd random number.) However, I'm running into problems.
I suspected that the form was re-generating the numbers every time the form POSTED and the input was collected, so I tried using sessions instead to keep those numbers persistent. It's a mess to say the least.
I found this existing post: Problems with guess a number game , but the solution didn't remedy my problem.
<?php
if(empty($_POST))
{
$_SESSION['$number1'] = Rand(0, 100);
$_SESSION['$number2'] = Rand(0, 100);
}
if($_POST["submit"])
{
$input = $_POST['input'];
if($input == ($_SESSION['$number1'] + $_SESSION['$number2']))
{
echo "Correct! ";
}
else
{
echo "Incorrect! ";
}
}
echo "<hr><br> What is... <b>" . $_SESSION['$number1'] . " + " . $_SESSION['$number2'] . "</b>";
?>
<form action="" method="post">
<input type="text" name="input">
<input type="submit" name="submit">
</form>
<?php
echo "<b>DEBUG ANSWER: </b> " . ($_SESSION['$number1'] + $_SESSION['$number2']);
?>
Any help would be appreciated!

Answer 1

I changed a few things, personally, I wouldn't use the session, rather user hidden inputs. (if you're worried about security.. you shouldn't be.. numbers game, not banking site)
<?php
//Create a function to generate the random numbers (So we can re-use it)
function generateNumbers()
{
$one = Rand(0, 100);
$two = Rand(0, 100);
//Now return the random numbers
return array('number1' => $one, 'number2' => $two);
}
//Check if the submit button has been clicked
if($_POST["submit"])
{
$input = $_POST['input'];
if($input == $_POST['number1'] + $_POST['number2'])
{
echo "Correct! ";
}
else
{
echo "Incorrect! ";
}
}
//Now we create the numbers
$numbers = generateNumbers();
echo "<hr><br> What is... <b>" . $numbers['number1'] . " + " . $numbers['number2'] . "</b>";
?>
<form action="" method="post">
<input type="text" name="input">
<input type="submit" name="submit">
<!-- Personally I would rather use hidden inputs, than use the session -->
<input type="hidden" name="number1" value="<?php echo $numbers['number1'] ?>" />
<input type="hidden" name="number2" value="<?php echo $numbers['number2'] ?>" />
</form>
<?php
echo "<b>DEBUG ANSWER: </b> " . ($numbers['number1'] + $numbers['number2']);
?>