為什么數據不顯示php mysql

Question

嘗試在index.php上顯示數據，用戶名運行良好，電子郵件未顯示。

server.php

$query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
$results = mysqli_query($db, $query);
if (mysqli_num_rows($results) == 1) {


  $_SESSION['email'] = $email;
  $_SESSION['username'] = $username;
  $_SESSION['success'] = "You are now logged in";
  header('location: index.php');

的index.php

<?php
// Echo session variables that were set on previous page
echo "Your email is: " . $_SESSION['email'] . "<br>";
echo "Your username is: " . $_SESSION['username'] . "";
?>

Answer 1

查詢數據后，您沒有獲取結果。 使用mysqli_fetch_assoc

請注意 ，我已將mysqli_real_escape_string應用到您的WHERE條件參數，以解決與SQL注入相關的問題。 雖然這不是萬無一失的解決方案！

更改為以下內容：

$query = "SELECT * 
          FROM users 
          WHERE username = '" . mysqli_real_escape_string($db, $username) . 
          " AND password = '" . mysqli_real_escape_string($db, $password) . "'";
$results = mysqli_query($db, $query);
if (mysqli_num_rows($results) == 1) {

  $row = mysqli_fetch_assoc($db, $results);
  $_SESSION['email'] = $row['email'];
  $_SESSION['username'] =  $row['username'];
  $_SESSION['success'] = "You are now logged in";

請閱讀有關如何使用“准備好的語句”防止SQL注入相關問題的信息 。

Answer 2

這是完整的代碼，出現$ username（已使用其他用戶測試）

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) {
    $password = md5($password);
    $query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
    $results = mysqli_query($db, $query);
    if (mysqli_num_rows($results) == 1) {


      $_SESSION['email'] = $email;
      $_SESSION['username'] = $username;
      $_SESSION['success'] = "You are now logged in";
      header('location: index.php');
    }else {
        array_push($errors, "Wrong username or password combination");
    }
  }
}

Answer 3

您沒有從結果中獲取電子郵件，因此$ email變量為null。 如果電子郵件在您的用戶表中，則需要從結果中進行分配。