I have this code:

Code:
    <?php
    // *** Validate request to login to this site.
    if (!isset($_SESSION)) {
      session_start();
    }
    
    $loginFormAction = $_SERVER['PHP_SELF'];
    if (isset($_GET['accesscheck'])) {
      $_SESSION['PrevUrl'] = "index.html";
    }
    // Declaring variables
    if (isset($_POST['correo'])) {
      $loginUsername=$_POST['correo'];
...