如果单击提交按钮，则在PHP代码中更新变量的值

I'm doing a simple form where there are two text boxes and when I input the values and click the button, the entered values would be set/updated to the variables in the php code. It updates the values but for that session only and if I refresh the page, I need to input the values again.

When I click submit, it would not show any error and is internally updated but the old/default values of the variables is still there.`

<div class="modal-body">
  <form action="/editUser.php" method="POST">
    <table>
      <tr>
        <td>E-mail:</td>
        <td><input type="text" name="emailChange" autocomplete="off" required></td>
      </tr>
      <tr>
        <td>Hash Key:</td>
        <td><input type="text" name="hashChange" autocomplete="off" required></td>
      </tr>
    </table>

    <input type="submit" name="submitEdit" class="btn btn-success btn-sm acceptbtn" value="Change Value">
  </form>
</div>


<?php 
//edit username and hash
$username = "aaronferrerquitoriano@gmail.com";
$hash = "4a95acef14a537bb3d32bc6aad8cb80baa9d18f9ac06b3158f50784e6735c4c6";
if(isset($_POST['submitEdit'])){
$username = $_POST['emailChange'];
$hash = $_POST['hashChange'];
}
?>

</div>

In place of your php, use this code.

<?php 
if(!isset($_POST['submitEdit'])){
$username = "aaronferrerquitoriano@gmail.com";
$hash = "4a95acef14a537bb3d32bc6aad8cb80baa9d18f9ac06b3158f50784e6735c4c6";
}
if(isset($_POST['submitEdit'])){
$username = $_POST['emailChange'];
$hash = $_POST['hashChange'];
}
?>

Hope this would help you.