Simple Authorization via Database in PHP

Let's implement the simplest authorization based on a database, for now without registration. Instead of registering users, we will simply enter their logins and passwords into a table in the database:

Now let's create a form where the login and password will be entered:

login.php<form action="" method="POST">
  <input name="login">
  <input name="password" type="password">
  <input type="submit">
</form>

Now let's write the code that will check if the form has been submitted and, if so, check if there is a user in the database with that login and password:

login.php<?php
  if (!empty($_POST['password']) and !empty($_POST['login'])) {
    $login = $_POST['login'];
    $password = $_POST['password'];
    
    $query = "SELECT * FROM users WHERE login='$login' AND password='$password'";
    $res = mysqli_query($link, $query);
    $user = mysqli_fetch_assoc($res);
    
    if (!empty($user)) {
      // user is authorized
    } else {
      // incorrect login or password
    }
  }
?>