屏幕之间的PHP会话不持久

Question

I have come across an issue that has confused me a lot. I am working on a login screen using PHP and MySQL. I manage to validate the username and password against an existing user in the database and after this, I initiate a session, and set the session variable username to the username provided in the login screen.

    $username = html($_POST['username']);
    $password = html($_POST['password']);

    $result = $pdo->prepare('SELECT * FROM users WHERE username = :username  AND    password = :password');
    $result->bindValue(':username', $username);
    $result->bindValue(':password', $password);
    $result->execute();

    foreach($result as $user)
    {
        $count = $count + 1;
    }

    if ($count == 1)
    {
              session_start();
          $_SESSION['username'] = $username;
       ` //if I do an echo $_SESSION['username'] it displays the correct user
          header('Location: .');
          exit();`
    }

However when it transfers me to the index.php page the $_SESSION['username'] variable has disappeared and I do not understand why. This is the code I use in index.php to check for the username:

<p><a href="view.php">View all tasks</a></p>
<p><a href="form.php?add">Add your own task</a></p>

<p>Welcome, <?php echo $_SESSION['username']; ?></p>

however I get the following error: Notice: Undefined variable: _SESSION in C:\\xampp\\htdocs\\abcabcabc\\index.php on line 16

All advice will be greatly appreciated guys

Answer 1

将sesssion_start()添加到使用会话的所有脚本中

Answer 2

You must use session_start(); at the beginning of index.php file.

Answer 3

The first 2 answers are correct. You must start session on each page. I usually just put it in a file that is "included" in every page already (like a header file) so I don't have to think about it.