PHP Session Security: Preventing Session Hijacking

PHP Session Security: How to Avoid Session Hijacking

PHP Session Security - How to Avoid Session Hijacking

PHP session security is a crucial aspect of web application security. It involves implementing measures to protect user session data from unauthorized access, tampering, and theft.

PHP is the most applied programming language in web and application development, and as such, mechanisms must be put in place to secure user sessions from potential vulnerabilities.

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This guide will explain the significance of PHP session security in protecting your session data, examine the typical session attack and provide active practices to secure PHP sessions.

  • PHP sessions are essential for maintaining user-specific data across multiple website pages.
  • However, session hijacking and fixation attacks can compromise the security of the session data.
  • To ensure session security, developers must use secure session management practices such as:
    • Generating a unique session ID for each user
    • Regenerating the session iD after login and logout
    • Using HTTPS encryption for transmitting session data
    • Setting session timeouts to expire inactive sessions automatically
    • Securely storing session data, such as a database or encrypted files
    • Developers should also implement additional security measures such as input validation, authentication, and access control to prevent attacks on session data.
  • Types of session attacks include session hijacking, XSS, session fixation, and session sniffing.

What Are  PHP Sessions?

Sessions are pages or activities a user performs on a site at a time. In PHP, a session is a way to store information about a user across different pages or requests. Sessions are commonly used to store information such as login credentials, shopping cart contents, user preferences, and other data that need to persist across multiple page views.

PHP develops on HTTP-generated cookies to create a framework that maintains context across various users’ requests. PHP generates a PHPSESSID cookie with a session ID and stores it in a file whenever a session is started on a site. Should that session be reopened on the user’s browser, the server will link it with the previous session data and continue from where the user stopped, resulting in a continuous session state.

Importance of PHP Session Security

Final: PHP Session Security: How to Avoid Session Hijacking

PHP session security is crucial for protecting sensitive user data and preventing unauthorized access to web applications. Here are some of the reasons why PHP session security is essential:

1. Preventing Session Hijacking

PHP session security prevents users in a session from being hijacked and losing control of their session. Without proper security measures, attackers can easily hijack a user’s session and gain access to their sensitive information or perform malicious actions on their behalf.

In a world of increased cyber crimes, attackers need to have significant knowledge of a user cookie session to hack such a session. PHP session security helps safeguard these sessions from attacks.

2. Protecting User Privacy

Sessions often contain personal information login by users, including usernames, passwords, and other sensitive data. Ensuring adequate and proper session security helps prevent this information from falling into the wrong hands.

3. Compliance

Organizations and industrial bodies across the European Union (EU) are subject to local privacy laws and data protection regulations, such as General Data Protection Regulation (GDPR) and the Health Insurance Portability and Accountability Act (HIPAA), to protect customer privacy as regards personal and sensitive information. Ensuring proper session security is a key component of compliance with these regulations.

4. Maintaining Trust

A compromise of a user’s information can be detrimental to both the user and the organization. For example, suppose a user’s data is compromised due to poor session security. In that case, it can lead to a loss of trust in the application and potentially harm the reputation of the organization behind it.

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Types of Session Attacks

Users are placed at several security risks without excellent and appropriate session security. A variety of session attacks and vulnerabilities can compromise PHP security. Some of them are:

1. Session Fixation

Session fixation occurs when an attacker tries to set a user’s session ID to a known value that can be used across platforms and without appropriate expiry measures. Cybercriminals perform session fixation by adding to the session ID in the URL variable of a specific session ID. Once a user continues that session, hackers can easily hijack it and use the credentials to log in to the user’s account.

2. Session Hijacking

Session hijacking occurs when attackers try to obtain a user’s session ID, either by eavesdropping on network traffic or by stealing through other means. The cookies employed for storing session IDs must be perfectly secured as insecure session cookies offer hackers easy predictability of a user session ID.

If attackers have a user session ID, they can use it to impersonate users by performing malicious transactions, which can also lead to the loss of sensitive information.

3. Session Sniffing

In plaintext, session sniffing happens when attackers use packet sniffers or other tools to intercept network traffic and capture session IDs. Using packet sniffers, a hacker can monitor the traffic within a network, confirm if the session is accurate, and intercept the user’s session cookies.

Session sniffing is sometimes called a man-in-the-middle attack, as the attacker is usually stationed between the source and destination of the traffic. Session keys obtained from packet sniffing are used to impersonate users to perform certain activities within the application.

4. Cross-Site Scripting (XSS)

Cross-site scripting occurs when attackers inject malicious scripts into web pages of a website that can steal session IDs or perform other hostile actions. For example, when a website uses unclear or non-sanitized GET variables, attackers can apply javascript in a GET request and infuse it into the web page’s body. This grants them equal access to the website’s own JavaScript and can derive the PHPSESSID cookie from the server.

5. Cross-Site Request Forgery (CSRF)

Cross-site request forgery occurs when attackers trick users into unknowingly making requests to a web application, which can be used for unauthorized actions on the user’s behalf. Cross-site request forgery is mostly permission due to a vulnerability in the application, mainly when the programmer did not perform due diligence in checking where the request was sent from.

Common PHP Session Security Issues

Final: PHP Session Security: How to Avoid Session Hijacking

PHP session security issues can be a significant vulnerability for web applications, allowing attackers to hijack user sessions and gain unauthorized access to sensitive data. Some common PHP session security issues include:

1. Session Hijacking

Session hijacking is the most common PHP session security issue. It reflows which an attacker obtains access to a user’s session. Theoretically, an attacker can get a user session ID by predicting or brute force (guessing). However, stealing a session ID is more paramount than guessing or predicting is less likely to occur.

Once an attacker obtains a user session ID, he uses the ID to get full access to other sessions. A session ID has the propensity to enable the server to give full access to the respective account of a user, hence, using it to impersonate the user.

2. Session Fixation

The secrecy of the session identifier is of utmost concern when discussing sessions. When a session identifier is kept secret, session hijacking becomes difficult. Session fixation occurs when an attacker tricks a user into using a session identifier the attacker selects.

A session fixation attack can come in the form of links, protocol-level redirects, or a refresh header issued as an HTTP header. The attacker’s primary goal is to trick the user into visiting a URL with the attacker’s session identifier.

3. Session Replay

A session replay occurs when an attacker intercepts a user’s session data and uses it to replay the session later. The cybercriminal eavesdrops on a secure network community and aims to intercept and maliciously delay or resend it to trick the receiver into performing actions the attacker wants.

4. Cross-Site Scripting (XSS)

Cross-site scripting is a vulnerability issue with PHP sessions whereby a programmer does not save an input before extending it to the web browser. Attackers primarily use XSS to inject malicious code into a web page that can steal session IDs or other sensitive information.

For instance, a blog allows users to input comments possessing HTML tags, but the blog’s script does cancel out tags, enabling users to run JavaScript on the page. A cybercriminal can use this by encoding JavaScript in the browser, thus stealing the user’s session cookies.

5. Cross-Site Request Forgery (CSRF)

Cross-site request forgery is a PHP session security vulnerability that tricks a web visitor into making unauthorized requests. For example, when a website sends an information request to another website on the recommendation of a user, along with the user’s session cookie, a hacker can send in a cross-site request forgery attack, which truncates the trustful relationship between the user’s browser and the web server.

Sometimes the attacker may gain complete control of the user’s account, accessing all the application functionality and data. This can become highly damaging to both the user and the organization.

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Best Practices for PHP Session Security

Final: PHP Session Security: How to Avoid Session Hijacking

There are a variety of measures you can employ to prevent attackers from gaining access to a user’s session ID and session data. Here are some of the best practices for PHP session security:

1. Use HTTPS

HTTPS is an encrypted protocol that provides a secure communication channel between the client and the server. Always ensure that web applications, servers, and SSO systems use HTTPS. Data flow should be properly encrypted to ensure sessions are secured at every stage to prevent the interception of session data.

Web developers and programmers must also use robust client-side defenses to shield a user’s browser and session cookies from XSS attacks.

2. Use Session_Regenerate_Id() Function

Session IDs are the keys to accessing session data. To prevent session fixation attacks, you should regenerate the session ID frequently after their initial authentication. This makes the session ID curled by the attacker useless because it changes immediately.

To regularly regenerate session IDs, PHP has a session_regenerate_id() function that generates a new session ID to replace the one previously used. This function also deletes the old session and every associated session data. However,

3. Use Strong Session IDs

Session ID should be generated randomly to make it difficult for an attacker to guess a valid session ID correctly. If a cybercriminal successfully guesses a user session, he can access the user account and other personal information freely.

To prevent this, generate strong session IDs with random numbers and alphabets to make it difficult for attackers to guess the session ID. You can also use a cryptographically secure pseudorandom number generator (CSPRNG) to generate session IDs.

4. Limit Session Lifetime

The time a user can remain inactive before their session expires should be limited. Setting the session lifetime to a reasonable duration ensures that the session is not left open for an extended period. On the other hand, if the session’s lifetime is too long, it may increase the risk of hijacking attacks.

Use the session_set_cookie_params() function in PHP to set the session duration. This function embodies three parameters – lifetime (the time taken before a cookie expires), path (the cookies directory), and domain (the domain where the cookie would be valid). Set the lifetime parameter to a reasonable duration.

5. Destroy the Session Data after Logout

After a user, every session variable associated with the user must be destroyed. This prevents any sensitive data stored in the session from hijacking attacks. It also prevents the user’s information from being accessed by anyone who may use the same device after the user has logged out.

To destroy a PHP session, use the session_destroy() function. Thisunsetstion unsets and clears all the session cookies on the client side and deletes the session file from the server.

6. Store Session Data Securely

Storing session data in a database offers extra later protection for users’ sessions. Sessions stored in the database are not accessible to anyone, irrespective of their gaining access to the server file system. In addition, it allows for flexibility when compiling user sessions. For instance, you can track user activity across multiple servers through a centralized database.

Moreover, if you need to delete or expire a session, you can seamlessly do this using SQL queries. Also, databases are created to handle large data amounts excellently, making them the right point for storing session variables.

7. Use Secure Cookies

Secure cookies prevent session hijacking attacks by restricting the transmission of cookies to restrict your browser from exposing the cookie through channels other than HTTP. You need to set the cookie to an HTTPOnly response header.

This measure helps prevent cloned scripts from hijacking user sessions and stealing session cookies. For example, to activate HTTPOnly for PHP session variables, insert the code session.cookie_httponly = 1 into the php.ini file.

8. Use Token-Based Authentication

Token-based- based authentication is a secure way to manage user authentication and prevent session hijacking attacks. A token-based authentication infuses a specific token in a request from a client, which is then verified by the server.

The token is generated via a cryptographic algorithm and is cryptographically tracked, so any tampering can be easily detected. In addition, tokens ensure user session data is secure because only authorized requests are processed through the server.

9. Validate Session Data

Validating the session data before using it in your application helps prevent session fixation attacks. This implies that any user input, either through GET parameters, forms, or other means, needs to be validated and sanitized before usage. Two main functions in PHP can be used to sanitize inputs – strip_tags() and htmlspecialchars(). strip_tags() simply removes all HTML tags, including <script> tag and htmlspecialchars() converts special characters into HTML entities.

10. Keep PHP Up-To-Date

Updated versions of PHP often come with the latest security patches to prevent known vulnerabilities. If you’re operating with an outdated version, hackers can easily take advantage of the inherent vulnerabilities. PHP versions are usually set at the server level. Hence you may need to contact your hosting provider for an updated version.


Web developers, programmers, and organizations all over the world have an essential part to play in ensuring that the use of their applications, website, and other devices are free from session hijacking. Therefore, cyber security is paramount, and taking adequate care to maintain users’ sensitive information safety should be done with due diligence.

Since PHP is widely used across websites worldwide, measures must be taken to ensure PHP session security. This article has highlighted some common PHP session attacks and provided practices to help prevent them. Go through and put them into practice.

Next Steps: What Now?

Learn More About PHP

Frequently Asked Questions

How can you ensure PHP session security?

One way to avoid session hijacking is to use a strong session ID value with enough entropy. The OWASP Cheat Sheet recommends using at least 64 bits of entropy for the session ID value. This can be achieved by using a good PRNG (pseudo-random number generator).

What is a session in PHP?

A session in PHP is a way to store information about a user across multiple pages or requests on a website. For example, when users log in, their information is stored in a session variable that can be accessed on subsequent pages. This allows the user to navigate the website without constantly logging in again.

What is the session_destroy function?

It is important to use the session_destroy function to ensure PHP session security. This function terminates a session and deletes all data associated with it. It is recommended to call this function when a user logs out or after a certain period of inactivity.

What is PHP session implementation?

PHP session implementation is a way to store data across multiple requests from the same user. For example, when a user logs in to a website, the server creates a unique session ID and keeps it in a cookie on the user’s browser. This session ID is used to identify the user’s session on subsequent requests.

Can session management help secure session resources?

Yes! Session management can prevent the consumption of much security in a session. Session management systems should bear light resources so that attacks such as DDos that enter the system with malicious requests don’t use a considerable amount of resources.

Is preventing session hijacking important for business?

Session hijacking is one of the most dangerous cyberattacks because cyber criminals have unauthorized access to customers’ or employees’ accounts or data. This can devastate businesses as it may incur legal liabilities, reputation damage, and financial losses.

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