How to use PHP forms to prevent unauthorized access attacks

With the continuous development of Internet technology, network security issues have attracted increasing attention. Among them, unauthorized access attacks are a common network security threat that can be prevented through PHP forms. This article will introduce the basic concepts of PHP forms and how to use PHP forms to prevent unauthorized access attacks.

1. Basic concepts of PHP forms

PHP forms are a server-side technology used for website development. It can interact with databases and servers by embedding PHP code in HTML pages. . PHP forms generally include the following elements:

1. Form HTML code

Form HTML code is the basic web form element, including form name, form elements and form actions, etc. . Form elements can be input boxes, drop-down boxes, text areas, etc. Form actions can be submit the form, reset the form, etc.

2. PHP script

PHP script is a bridge connecting the form and the server. It can process the data submitted by the form and store it in the database or feed it back to the user. The PHP script must be in the same file as the HTML form.

3. Database connection

PHP forms generally need to be connected to the database, and extensions such as mysqli or PDO can be used to connect. After connection, operations such as data query, insertion, update, and deletion can be performed.

2. How to prevent unauthorized access attacks

Unauthorized access attacks refer to attackers illegally accessing certain resources or functions of the website through some means, such as brute force password cracking and URL tampering. Access sensitive data of the website through other methods. Here are several effective PHP form methods to prevent unauthorized access attacks:

1. session verification

By using session verification in PHP scripts, you can ensure that users must first Only through login authorization can you access sensitive resources or functions of the website. Session is a server-side storage technology that enables user authentication by storing some user information in the session.

Session verification code can be written at the top of the PHP script, for example:

<?php
session_start();
if(!isset($_SESSION['username'])){
header('Location: login.php');
exit();
}
?>

The function of this code is to check whether there is a session variable named username, and if it does not exist, redirect to log in page.

2. CSRF Protection

CSRF is the abbreviation of cross-site request forgery and is a common network attack method. Attackers construct forged HTTP requests to illegally access and operate the target website.

In PHP forms, CSRF attacks can be prevented by using CSRF tokens. CSRF token is a generated random string that is stored in the user's cookie or session. When the form is submitted, this token value is submitted to the server for verification to ensure the legitimacy of the request.

The code to generate the token value can be written in a PHP script, for example:

<?php
session_start();
$token = md5(uniqid(rand(), true));
$_SESSION['token'] = $token;
?>

The function of this code is to generate a random token value and store the value in the session.

In the form, the token value can be submitted to the server side through the hidden field, for example:

<form action="submit_form.php" method="post">
<input type="hidden" name="token" value="<?php echo $_SESSION['token']; ?>">
<!-- 其他表单元素 -->
</form>

On the server side, the CSRF token can be verified through the following code:

<?php
session_start();
if($_POST['token']!==$_SESSION['token']){
die("非法请求");
}
?>

The purpose of this code is to check whether the submitted token value matches the token value in the session. If they do not match, the request is rejected.

3. Input validation

By validating user input in PHP forms, you can effectively prevent SQL injection, XSS and other attacks. In PHP forms, you can use functions such as filter_var and preg_match for input verification, such as:

$name = $_POST['name']; //获取用户输入
if(!preg_match("/^[a-zA-Z0-9_]{3,15}$/",$name)){
die("用户名格式错误"); //验证用户名格式是否正确
}

The function of this code is to use the preg_match function to verify whether the user name format is correct.

During input verification, appropriate functions and regular expressions need to be selected according to the specific situation to ensure the security of user input.

Conclusion

PHP forms can effectively prevent unauthorized access attacks, thereby improving the security of the website. This article introduces the basic concepts of PHP forms and methods to prevent unauthorized access attacks. I hope it will be helpful to PHP developers.

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