我正在尝试为基于 Web 的 MIS 编写登录身份验证。下面是我使用的代码。但是，当给定用户名“admin”和密码“12345”时，即使该记录已放入数据表中，它也不会登录。
这是表的 SQL 代码：
CREATE TABLE accounts (
id INTEGER UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
username VARCHAR(255) NOT NULL UNIQUE,
password CHAR(32) NOT NULL,
last_login DATETIME NOT NULL
);
当我把echo $stmt->num_rows;0 返回时，我猜这意味着它在数据库中找不到匹配项。谁能帮我吗？
这是我的代码：
<?php
// Sanitize incoming username and password
$username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
$password = filter_var($_POST['password'], FILTER_SANITIZE_STRING);
// Connect to the MySQL server
$db = new mysqli("localhost", "root", "qwerty", "MIS");
// Determine whether an account exists matching this username and password
$stmt = $db->prepare("SELECT id FROM accounts WHERE username = ? and password = md5(?)");
// Bind the input parameters to the prepared statement
$stmt->bind_param('ss', $username, $password);
// Execute the query
$stmt->execute();
// Store the result so we can determine how many rows have been returned
$stmt->store_result();
if ($stmt->num_rows == 1) {
// Bind the returned user ID to the $id variable
$stmt->bind_result($id);
$stmt->fetch();
// Update the account's last_login column
$stmt = $db->prepare("UPDATE accounts SET last_login = NOW() WHERE id = ?");
$stmt->bind_param('d', $id);
$stmt->execute();
session_start();
$_SESSION['username'] = $username;
// Redirect the user to the home page
header('Location: http://localhost/');
}
?>