title: Difference between array_key_exists("id", $_SESSION ) and $_SESSION['id];
body: <p>in this code</p>
  
  <pre><code>if ((array_key_exists("id", $_SESSION) AND $_SESSION['id']) OR (array_key_exists("id", $_COOKIE) AND $_COOKIE['id'])) {
  
      header("Location: loggedPage.php");
  
  }
  </code></pre>
  
  <p>I dont know different between them. Can someone explain it to me?</p>
  
  <p>Thanks</p>
  
  <p>Minh Phuc</p>