How to process form data in PHP forms and prevent illegal attacks

With the development of the Internet, forms have become an indispensable part of the website. Forms allow users to easily enter data, submit data, and perform data queries. Developing forms is easier in PHP, but handling form data requires special attention. This article will introduce how to handle form data in PHP forms and prevent illegal attacks.

1. Get form data

The simplest way to get form data in PHP is to use the super global variable $_POST. $_POST is used to collect form data from the HTTP POST method. However, to avoid the program crashing unexpectedly, we need to use the PHP isset() function to check if the variable is set and not NULL.

Code example:

<?php
if(isset($_POST['submit'])){
   $name = $_POST['name'];
   $email = $_POST['email'];
   $message = $_POST['message'];
}
?>

The above code first uses the isset() function to check whether the user clicked the submit button. If this condition is true, the name, email, and message values ​​in $_POST will be saved to the corresponding variables.

2. Filter and clean the form data

After obtaining the form data, we need to filter and clean it. This is a very important step for security as users can easily enter anything in the form fields, including illegal and harmful content. Therefore, if we do not filter and clean form data, it may lead to some security issues such as SQL injection, cross-site scripting, etc.

In PHP, you can use filter functions to filter and clean form data. Filter functions in PHP are provided by extensions. You should ensure that extensions including php_filter and php_sanitize are enabled.

Sample code:

<?php
if(isset($_POST['submit'])){
   $name = filter_var($_POST["name"], FILTER_SANITIZE_STRING);
   $email = filter_var($_POST["email"], FILTER_SANITIZE_EMAIL);
   $message = filter_var($_POST["message"], FILTER_SANITIZE_STRING);
}
?>

The above code uses PHP's filter_var() function to filter and clean form data. The FILTER_SANITIZE_STRING filter removes HTML tags from strings. The FILTER_SANITIZE_EMAIL filter removes all illegal characters from email addresses.

3. Prevent illegal attacks

When processing form data, we must pay attention to security issues. The data passed to PHP may contain harmful content, so it must be checked and made sure it has the expected data type and format.

Here are some common types of security attacks and how to protect against them:

1. SQL injection

SQL injection is a common attack Way. Intruders can send malicious code to your database through form fields, thereby tampering with data or damaging the entire website.

Protection method:

Use prepared statements, such as PDO or MySQLi. This will automatically escape any user-entered characters, protecting your database from SQL injection attacks.

2. Cross-site scripting (XSS)

The purpose of a cross-site scripting attack is to inject malicious scripts into the user's browser to steal the user's data or attack the website.

Prevention method:

Use HTML/CSS filters to filter HTML tags entered by users, and use the htmlentities() or htmlspecialchars() function to escape special characters in user input.

3. CSRF attack

CSRF attack is an attack method in which the attacker deceives the user to change the user's settings or settings without the user's knowledge. operate.

Prevention method:

Use CSRF token to protect your form. Tokens make attacks more difficult by making it difficult for an attacker to impersonate the form.

4. HTTP Assertion Attack

In an HTTP assertion attack, an attacker can exploit a flaw in an HTTP header to gain control of or gain access to your website. An attacker can use methods such as "PUT", "DELETE", or "CONNECT" to tamper with your data or update files.

Prevention methods:

Use GET and POST methods to access and update data, and restrict your server to accept PUT, DELETE and other non-standard HTTP request methods.

Conclusion

In the process of PHP form processing, data filtering and cleaning are necessary steps to prevent various attacks. We have to validate the form data type and make sure the data entered is good. Be aware of security, which must be considered when handling form data. It is recommended to use prepared statements and limit request methods to protect the security of your data and website.

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