I tried to create a login page using javascript as seen below

我尝试使用如下所示的Java脚本创建登录页面

<script src="https://code.jquery.com/jquery-3.6.0.min.js">
  function myfunction(){
    var username = document.getElementById('username').value;
    var password = document.getElementById('password').value;

    jQuery.ajax({
      type: "POST",
      url: 'http://localhost/Gardening-System/select_user.php',
      dataType: 'json',
      data: {uname: username, psw: password },

      success: function (obj, textstatus) {
        if (!('error' in obj)) {
          var user = obj.result; // Define user variable here
          document.cookie = "username=" + username; // Set the cookie
          window.alert("Logged in as: " + username); // Display the logged-in username in an alert
          window.location.href = "index.html";
        } else {
          console.log(obj.error);
        }
      },
      
      error: function (xhr, status, error) {
        window.alert("AJAX request failed: " + error); // Handle AJAX request errors
      }
    });
  }
</script>

This is select_user.php which is to search the a database and checks whether the user exists. If they do, then it is supposed to return the username back to Javascript, which will then set the username as part of the cookie.

这是select_user.php，用于搜索数据库并检查用户是否存在。如果他们这样做，那么它应该将用户名返回给JavaScript，然后Javascript将用户名设置为cookie的一部分。

<?php
header('Content-type: application/json');

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $uname = $_POST['uname'];
    $psw = $_POST['psw'];

    // Database details
    // Localhost address
    $username = "root";
    $password = "";
    $dbname = "Gardening_System";

    // Creating a connection
    $con = mysqli_connect($host, $username, $password, $dbname);
    // echo ("checkpoint 1");

    // Ensuring connection is made
    if (!$con) {
        die("Connection failed: " . mysqli_connect_error());
    }

    // Sanitize user inputs to prevent SQL injection
    $uname = mysqli_real_escape_string($con, $uname);
    $psw = mysqli_real_escape_string($con, $psw);

    // Checking if the username and password combination exists in the database
    $checkQuery = "SELECT * FROM Username_Password WHERE username= '$uname' AND password= '$psw'";
    // mysqli_stmt_bind_param($stmt, "ss", $uname, $psw);
    // mysqli_stmt_execute($stmt);
    $checkResult = mysqli_query($con, $checkQuery);
    // echo ("checkpoint 2");

    if (mysqli_num_rows($checkResult) > 0) {
        $userData = mysqli_fetch_assoc($checkResult);
        $response = array('success' => true, 'result' => $userData["username"]);
        echo json_encode($response);
        // echo ("checkpoint 3");
        if (setcookie($uname)){
            header("Location: http://localhost/Gardening-System/index.html");
        }
    } else {
        // Return an error message in JSON format
        $response = array('error' => 'User does not exist');
        echo json_encode($response);
    }

    mysqli_close($con);
} else {
    // If the request method is not POST, return an error message
    $response = array('error' => 'Invalid request method');
    echo json_encode($response);
}
?>

After trying to login, it goes to the main screen, but it doesn't save the cookie and display it.

在尝试登录后，它会进入主屏幕，但不会保存并显示Cookie。