使用javascript刷新未设置的按钮？

I am making a calculator that will display the results on the same page, but when I refresh the button is still 'set' according to php. I have a function running to catch the refresh and stop such things in javascript for something else I was doing but I am not sure how to 'un-set' the button on refresh.

<script>
document.addEventListener("DOMContentLoaded", function() {
  hide();
});
function hide() {
    var x = document.getElementById('drinksDIV');
    x.style.display = 'none';
    var x = document.getElementById('submit');
    x.session_unset;
}
function enableDisable(bEnable, textBoxID)
{
    document.getElementById(textBoxID).disabled = !bEnable
}
function myFunction() {
    var x = document.getElementById('drinksDIV');
    if (x.style.display === 'none') {
        x.style.display = 'block';
    } else {
        x.style.display = 'none';
    }
}
</script>

But when I refresh the echo'd results still remain at the top

This is what i have at the top of my page:

<?php
if(isset($_POST['submit'])){ //check if form was submitted
  $input = $_POST['age']; //get input text
  echo "Success! You entered: ".$input;
}    
?>

Once submitted once it will always be there instead of hiding on refresh

If you don't want anything to show on your page after your PHP code is executed, you can do this:

<?php
if(isset($_POST['submit'])){ //check if form was submitted    
  $input = $_POST['age']; //get input text
  echo "Success! You entered: ".$input;
  die();
}    
?>

Note the die() function called after the echo.