почему данные не добавляются в БД вот код <?php $conn = mysqli_connect("localhost", "root", "", "blog") or die(mysqli_connect_error()); if (isset($_POST['submit'])) { if (!empty($username) && !empty($password)) { $username = mysqli_real_escape_string($conn, trim($_POST['username'])); $password = mysqli_real_escape_string($conn, trim($_POST['password'])); $query = "SELECT * FROM 'users' WHERE username = '$username'"; $data = mysqli_query($conn, $query); if ( mysqli_num_rows($data) == 0) { $query = "INSERT INTO 'users' (username , password) VALUES ('$username', '$password')"; $result = mysqli_query($conn, $query); if ($result) { echo 'Данные добавлены'; }else echo 'ошибка'; } } } ?> <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> </head> <body> <form action="auth.php" method="POST"> <input type="text" name = "username" placeholder="введите Имя Пользователя"> <br> <input type="text" name = "password" placeholder="Введите пароль"> <input type="submit" name = "submit" value="Вход"></input> </form> </body> </html>