How to Share Session Variables Between PHP Files for Secure CSRF Token Handling
June 12, 2024 ⚊ 3 Min read ⚊ PHPIn this tutorial, we will learn how to share session variables between PHP files, specifically focusing on handling a CSRF (Cross-Site Request Forgery) token securely. By the end of this tutorial, you will understand how to set a session variable in one PHP file and access it in another.
Prerequisites
- Basic knowledge of PHP
- Understanding of web sessions and how they work
- A local server environment like XAMPP, WAMP, or a remote server with PHP installed
Step 1: Setting Up Your Environment
Ensure you have a web server with PHP installed and running. If you’re working locally, tools like XAMPP or WAMP will help you set up a PHP environment quickly.
Step 2: Creating the First PHP File (A.php
)
This file will initialize the session and set the CSRF token.
- Start the session: This is crucial as sessions need to be started in any PHP file that accesses or modifies session variables.
- Generate a CSRF token: A secure random token is necessary to protect against CSRF attacks.
- Store the CSRF token in the session: This allows us to access the token from other PHP files.
Create a file named A.php
and add the following code:
<?php
// Start the session
session_start();
// Generate a CSRF token
$csrf_token = bin2hex(random_bytes(32));
// Register the CSRF token in the session
$_SESSION['csrf_token_registration'] = $csrf_token;
echo "CSRF token has been set.";
?>
Step 3: Creating the Second PHP File (B.php
)
This file will retrieve and use the CSRF token set in the session.
- Start the session: This is necessary to access session variables.
- Check if the CSRF token is set: Ensure the token exists before trying to use it.
- Retrieve and display the CSRF token: Access the token stored in the session and use it as needed.
Create a file named B.php
and add the following code:
<?php
// Start the session
session_start();
// Check if the CSRF token is set
if (isset($_SESSION['csrf_token_registration'])) {
$csrf_token = $_SESSION['csrf_token_registration'];
echo "CSRF Token: " . $csrf_token;
} else {
echo "CSRF token is not set.";
}
?>
Step 4: Testing the Implementation
- Run
A.php
: Open your browser and navigate toA.php
(e.g.,http://localhost/A.php
). You should see a message saying, “CSRF token has been set.” - Run
B.php
: Now, navigate toB.php
(e.g.,http://localhost/B.php
). You should see the CSRF token displayed on the screen.
Explanation
- Starting the session:
session_start()
initializes the session, making session variables accessible in the script. - Setting the session variable: In
A.php
, we generate a secure CSRF token usingbin2hex(random_bytes(32))
and store it in the session array$_SESSION['csrf_token_registration']
. - Accessing the session variable: In
B.php
, we check if$_SESSION['csrf_token_registration']
is set to ensure the token exists before trying to use it.
Tags:
- PHP session variables
- CSRF token handling in PHP
- Secure session management PHP
- Share session variables PHP
- PHP cross-site request forgery prevention