我已經用我的帳戶頁面制作了一個注冊系統。我可以在其中顯示名稱和密碼，但登錄后無法顯示電子郵件，因為我必須從 MySQL 數據庫中獲取它，因為用戶在登錄時沒有輸入他的電子郵件。代碼中沒有錯誤，但未顯示電子郵件。這是server.php登錄代碼：// LOGIN USER if (isset($_POST['login_user'])) {  $username = mysqli_real_escape_string($db, $_POST['username']);  $password = mysqli_real_escape_string($db, $_POST['password']);  if (empty($username)) {   array_push($errors, "Username is required");  }  if (empty($password)) {    array_push($errors, "Password is required");  }  if (count($errors) == 0) {    $password = base64_encode($password);    $query = "SELECT * FROM users WHERE username='$username' AND password='$password'";    $results = mysqli_query($db, $query);    if (mysqli_num_rows($results) == 1) {      $_SESSION['username'] = $username;//Here is the code with problem      $query = "SELECT email FROM users WHERE username='$username' AND password=''$password";      $result = mysqli_query($conn, $sql);    if (mysqli_num_rows($result) > 0) {    while($row = mysqli_fetch_assoc($result)) {        $_SESSION['email'] = $row["email"];    }    }//Here it ends      $_SESSION['password'] = $password;      $_SESSION['success'] = "You are now logged in";      if ($_SESSION['page'] == "account.php"){          header('location: account.php');      }      else{        header('location: index.php');      }    }else {        array_push($errors, "Wrong username/password combination");   }  }