Php Session Variable Deleted After Post - php

Question

This code is supposed to save a random number into a session varible when generateCode is pressed
It does generate it and store in the variable but when i try to acces is from the if(isset($_POST['confirmCode'])){ it is empty
<?php
session_start();
if(isset($_POST['generateCode'])){
$_SESSION["key"] = mt_rand(100000, 999999);
}
if(isset($_POST['confirmCode'])){
die($_SESSION["key"]);
}
?>
<form method="POST">
<input type="text" name="confcode" placeholder="Confirmation Code">
<input type="submit" name="confirmCode" value="Confirm">
<input type="submit" name="generateCode" value="Generate">
</div>
</div>
</form>
Does anybody know how i can make a variable that stays some time even after post request
Edit:
So to get this clear confirmCode is a button to submit the code entered in a <input type="text></input> But i decided to not include the code to get the content if confCode because this question is about how to keep a variable generated by mt_rand even after <input type="submit"> is pressed

Answer 1

The problem isn't the button, PHP actually puts the name and value in the parameters.
The problem is with the die function. It expects either a message (string) or a status code (integer). When you generate the random number it interprets the message as a number (status code) instead of a string (message). To make sure it interprets the key as a string you could wrap it in a strval() function like this:
die(strval($_SESSION["key"]));