php登录后返回原来页面

<?php
session_start();

if (empty($_SESSION['login_url'])) {
    $_SESSION['login_url'] = $_SERVER['REQUEST_URI'];
}
?>

<?php
session_start();

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    // 验证用户名和密码
    $username = $_POST['username'];
    $password = $_POST['password'];

    if (validate_user($username, $password)) {
        // 登录成功，重定向回原始URL
        header('Location: ' . $_SESSION['login_url']);
        exit();
    } else {
        echo "Invalid username or password";
    }
}
?>

<form method="post">
    Username: <input type="text" name="username"><br>
    Password: <input type="password" name="password"><br>
    <input type="submit" value="Login">
</form>

<?php
function validate_user($username, $password) {
    // 这里应该是数据库查询或其他验证逻辑
    return $username == 'admin' && $password == 'password';
}
?>