会话未被取消设置或销毁

session_start（） 在 Connect 中调用.php但出于安全原因未包含在此处

我在会话未取消设置或销毁时遇到问题

我有一个注销.php我在其中处理注销，它看起来像这样

<?
 if(isset($_POST['logout'])){
  session_start();
  session_unset();
  session_destroy();
  header("Location: index.php");
 }
?>

然后，我在导航中调用此代码，该代码工作正常，但是一旦我登录并尝试注销，导航应该消失并且应该显示表单，但导航是这里唯一显示的是该脚本

<nav>
<?
 if(isset($_SESSION['user'])){
  include("server/constants/nav.php");
 } else{?>
  <div class="form">
  <input type="button" id="displayLoginForm" onclick="showLogin()" value="Login">
  <input type="button" id="displayRegisterForm" onclick="showRegister()" value="Register">
   <div id="loginSection" style="display:none">
  <?  include("server/display/LoginForm.php") ?>
   </div>
   <div id="registerSection" style="display:none">
   <?  include("server/display/RegisterForm.php") ?>
   </div>
  </div>
<? } ?>
</nav>

其他相关脚本

句柄登录.php

<?
 if(isset($_POST['Login'])){
  $user = $_POST['username'];
  $pass = $_POST['password'];
  $sql = "SELECT * FROM energywise WHERE username='$user'";
  $query = mysql_query($sql);
  $row = mysql_fetch_object($query);
  $id = htmlspecialchars($row->id);
  $firstName = htmlspecialchars($row->firstname);
  $lastName = htmlspecialchars($row->lastname);
  $username = htmlspecialchars($row->username);
  $password = htmlspecialchars($row->password);
  $mail = htmlspecialchars($row->email);
  if(empty($id)){
   echo 'Account does not exist';
  } elseif($pass != $password){
   echo 'Passwords do not match';
  } else{
   $_SESSION['user'] = $id;
   header("Location: index.php");
  }
 }
?>

导航.php

<script src="http://code.jquery.com/jquery-latest.min.js" type="text/javascript"></script>
<link rel="stylesheet" href="css/navigation.css">
<script src="js/nav.js"></script>
<div id='cssmenu'>
<ul>
   <li class='active'><a href='index.php'>Home</a></li>
   <li><a href='calender.php'>Calender</a></li>
   <li><a href='locations.php'>Locations</a></li>
   <li><a href='#'>Placeholder</a></li>
   <form method="post">
   <li><input type="submit" name="logout" value="Logout"></li>
   </form>
</ul>