php登录注册修改密码代码

PHP 登录、注册和修改密码的基本流程可以分为以下几个步骤，这里提供一个简化版的示例：

1. **登录系统**:

// 连接数据库
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// 用户提交表单数据
$username = $_POST['username'];
$password = $_POST['password'];

// 验证用户名和密码是否匹配
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $username);
$stmt->execute();
$result = $stmt->get_result();

if ($result->num_rows == 1) {
    $row = $result->fetch_assoc();
    if (password_verify($password, $row['password'])) {
        // 登录成功，设置session或其他方式保持用户登录状态
        session_start();
        $_SESSION['user_id'] = $row['id'];
        header("Location: dashboard.php");
    } else {
        echo "Invalid password.";
    }
} else {
    echo "User not found.";
}
$stmt->close();
$conn->close();

2. **注册系统**:

if ($_SERVER["REQUEST_METHOD"] === "POST") {
    // 数据验证
    $username = trim($_POST['username']);
    // ... (对其他字段进行验证)
    
    $hashed_password = password_hash($_POST['password'], PASSWORD_DEFAULT);

    $stmt = $conn->prepare("INSERT INTO users (username, password) VALUES (?, ?)");
    $stmt->bind_param("ss", $username, $hashed_password);
    $stmt->execute();
    $stmt->close();
    // 注册成功后跳转到登录页面
    header("Location: login.php");
}

3. **修改密码**:

if ($_SERVER["REQUEST_METHOD"] === "POST") {
    // 获取当前登录用户的ID
    session_start();
    $userId = $_SESSION['user_id'];

    $oldPassword = $_POST['old_password'];
    $newPassword = $_POST['new_password'];

    // 验证旧密码，然后更新新密码
    $stmt = $conn->prepare("SELECT password FROM users WHERE id = ?");
    $stmt->bind_param("i", $userId);
    $stmt->execute();
    $row = $stmt->get_result()->fetch_assoc();
    if (password_verify($oldPassword, $row['password'])) {
        $hashed_new_password = password_hash($newPassword, PASSWORD_DEFAULT);
        $stmt = $conn->prepare("UPDATE users SET password=? WHERE id=?");
        $stmt->bind_param("si", $hashed_new_password, $userId);
        $stmt->execute();
        $stmt->close();
        // 密码更改成功，提示用户
        echo "Password updated successfully.";
    } else {
        echo "Old password is incorrect.";
    }
}

以上代码只是一个基本框架，实际应用中需要添加更多的错误处理和安全性措施，例如防止 SQL 注入、密码强度检查等。