php - 登录时保存 IP，如果 IP 更改则注销，PHP MySql

Question

请注意，我对 php 和 mysql 完全陌生， 现在我有一个完全正常工作的注册和登录系统。

我的mysql表如下所示:id用户名电子邮件密码ip

我想在每次登录时保存用户的IP，如果IP已更改，则自动注销他，这样如果他再次登录，新的IP将在数据库中更新。

这是我的 server.php

<?php
session_start();

// initializing variables
$username = "";
$email    = "";
$errors = array(); 

// connect to the database
$db = mysqli_connect('localhost', 'root', '', 'registration');

// REGISTER USER
if (isset($_POST['reg_user'])) {
  // receive all input values from the form
  $username = mysqli_real_escape_string($db, $_POST['username']);
  $email = mysqli_real_escape_string($db, $_POST['email']);
  $password_1 = mysqli_real_escape_string($db, $_POST['password_1']);
  $password_2 = mysqli_real_escape_string($db, $_POST['password_2']);

  // form validation: ensure that the form is correctly filled ...
  // by adding (array_push()) corresponding error unto $errors array
  if (empty($username)) { array_push($errors, "Username is required"); }
  if (empty($email)) { array_push($errors, "Email is required"); }
  if (empty($password_1)) { array_push($errors, "Password is required"); }
  if ($password_1 != $password_2) {
	array_push($errors, "The two passwords do not match");
  }

  // first check the database to make sure 
  // a user does not already exist with the same username and/or email
  $user_check_query = "SELECT * FROM users WHERE username='$username' OR email='$email' LIMIT 1";
  $result = mysqli_query($db, $user_check_query);
  $user = mysqli_fetch_assoc($result);
  
  if ($user) { // if user exists
    if ($user['username'] === $username) {
      array_push($errors, "Username already exists");
    }

    if ($user['email'] === $email) {
      array_push($errors, "Email already exists");
    }
  }

  // Finally, register user if there are no errors in the form
  if (count($errors) == 0) {
  	$password = md5($password_1);//encrypt the password before saving in the database

  	$query = "INSERT INTO users (username, email, password) 
  			  VALUES('$username', '$email', '$password')";
  	mysqli_query($db, $query);
  	$_SESSION['username'] = $username;
  	$_SESSION['success'] = "You are now logged in";
  	header('location: index.php');
  }
}

// ... 
// ... 

// LOGIN USER
if (isset($_POST['login_user'])) {
  $username = mysqli_real_escape_string($db, $_POST['username']);
  $password = mysqli_real_escape_string($db, $_POST['password']);

  if (empty($username)) {
  	array_push($errors, "Username is required");
  }
  if (empty($password)) {
  	array_push($errors, "Password is required");
  }

  if (count($errors) == 0) {
  	$password = md5($password);
  	$query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
  	$results = mysqli_query($db, $query);
  	if (mysqli_num_rows($results) == 1) {
  	  $_SESSION['username'] = $username;
  	  $_SESSION['success'] = "You are now logged in";
  	  header('location: index.php');
  	}else {
  		array_push($errors, "Wrong username or password combination");
  	}
  }
}

?>

Answer 1

用户登录后，您可能会为每个用户使用一个 php session 。下面是如何执行此操作的示例。 Using sessions & session variables in a PHP Login Script

为了满足您的需求，您可以从登录页面将 IP 地址隐藏在 session 中，如下所示。

$_SESSION['ip'] = $_SERVER['HTTP_X_FORWARDED_FOR'] 
             ? $_SERVER['HTTP_X_FORWARDED_FOR']
             : $_SERVER['REMOTE_ADDR'];

然后在其他页面上您可以执行此操作来检测 ip 更改。

$ip = $_SERVER['HTTP_X_FORWARDED_FOR'] 
             ? $_SERVER['HTTP_X_FORWARDED_FOR']
             : $_SERVER['REMOTE_ADDR'];
if (isset($_SESSION['ip']) && $ip != $_SESSION['ip']) {
    session_destroy();
    /* redirect to your login pagge */ 
}

几点:

1. 确保 session strict mode在您的 php 服务器上设置，因此 session_destroy() 有效。

2. 注意:用户的 IP 地址可以在事件 session 期间合法更改:DHCP 可以在用户不知情的情况下更改地址。很少见，但它确实发生了。

3. 如果您的用户位于机构(企业)，他们中的许多人似乎都具有相同的 IP 地址:您的网站看到的是他们的共享互联网网关的 IP 地址。

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因此，过于关注用户的 IP 地址有点危险。