blog php如何实现用户登录

在PHP中实现用户登录功能，通常需要以下几个步骤：

创建数据库表：首先需要在数据库中创建一个表来存储用户信息，包括用户名、密码等。

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(255) NOT NULL UNIQUE,
    password VARCHAR(255) NOT NULL
);

注册新用户：提供一个注册表单，让用户输入用户名和密码，然后将用户信息插入到数据库中。

<?php
// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// 注册新用户
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $username = $_POST["username"];
    $password = password_hash($_POST["password"], PASSWORD_DEFAULT);

    $sql = "INSERT INTO users (username, password) VALUES ('$username', '$password')";

    if ($conn->query($sql) === TRUE) {
        echo "New user registered successfully";
    } else {
        echo "Error: " . $sql . "<br>" . $conn->error;
    }
}

$conn->close();
?>

<!-- 注册表单 -->
<form action="" method="post">
    Username: <input type="text" name="username"><br>
    Password: <input type="password" name="password"><br>
    <input type="submit" value="Register">
</form>

用户登录：提供一个登录表单，让用户输入用户名和密码，然后验证用户信息是否与数据库中的记录匹配。

<?php
// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// 用户登录
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $username = $_POST["username"];
    $password = $_POST["password"];

    $sql = "SELECT * FROM users WHERE username='$username'";
    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        $row = $result->fetch_assoc();
        if (password_verify($password, $row["password"])) {
            // 登录成功，跳转到用户主页
            header("Location: user_home.php");
        } else {
            echo "Invalid password";
        }
    } else {
        echo "User not found";
    }
}

$conn->close();
?>

<!-- 登录表单 -->
<form action="" method="post">
    Username: <input type="text" name="username"><br>
    Password: <input type="password" name="password"><br>
    <input type="submit" value="Login">
</form>

保护用户资源：在用户登录后，可以通过session来保护用户资源，确保只有登录用户才能访问特定页面。

<?php
// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// 检查用户是否已登录
session_start();
if (!isset($_SESSION["loggedin"]) || !$_SESSION["loggedin"]) {
    header("Location: login.php");
    exit;
}

// 用户主页
echo "Welcome, " . $_SESSION["username"];
?>

这只是一个简单的示例，实际项目中可能需要考虑更多安全性和功能性问题。

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