How WordPress Handles Sessions and User Data in the Database

User Data Storage in WordPress 

wp_users Table 

The wp_users table stores the core user details: 

• ID: Unique identifier (auto-incrementing). 

• user_login: Username for login. 

• user_pass: A hashed password. 

• user_email: Email address. 

• user_nicename: URL-friendly version of the username. 

• user_registered: Registration timestamp. 

• user_status: (Rarely used) Legacy status flags. 

• display_name: Public display name. 

This table is lightweight and optimized for quick lookups, ensuring efficient authentication.

wp_usermeta Table 

The wp_usermeta table is where more extensive user data is stored. This table uses a key-value pair format to handle user-specific settings, plugin data, and roles: 

• umeta_id: Unique ID for the metadata entry. 

• user_id: Links to wp_users.ID. 

• meta_key: Name of the metadata field (e.g., first_name). 

• meta_value: The serialized value for the key. 

For example, user roles and capabilities (e.g., administrator or editor) are stored here under keys like wp_capabilities, and plugin-specific metadata can also be added to this table. WordPress offers the WP_User class to interact with user data. Methods like get() retrieve data from both the wp_users and wp_usermeta tables. 

In multisite setups, user capabilities may be stored per site (e.g., wp_2_capabilities), allowing users to have different roles across different sites in a network.

Session Management in WordPress 

WordPress does not rely on PHP’s $_SESSION superglobal to manage user sessions, which is a common approach in traditional PHP applications. Instead, WordPress uses authentication cookies and a database-backed session token system to manage sessions efficiently and securely. 

Authentication Cookies 

When a user logs in, WordPress generates two cookies: 

1. Authentication Cookie (wordpress_sec_[hash]): Stores the user ID, token, and expiration details for secure requests. 
2. Logged-in Cookie (wordpress_logged_in_[hash]): Similar, but used for non-secure requests. 

These cookies ensure that users remain logged in across sessions. By default, their expiration is set to 2 days, but if the “Remember Me” option is checked, they expire after 14 days. WordPress sets these cookies based on user login and manages them securely. 

Session Tokens and WP_Session_Tokens Class 

WordPress introduced the WP_Session_Tokens class in version 4.0 to manage session data without relying on PHP sessions. This class stores session tokens in the wp_usermeta table, specifically under the session_tokens meta key. Each session token includes: 

• expiration: Timestamp when the token expires. 

• ip: The user’s IP address. 

• ua: The user’s user agent (browser and OS details). 

• login: Timestamp of the login. 

When a user logs in, WordPress generates a token and stores it both in the authentication cookies and in the database. On subsequent requests, WordPress validates the session by comparing the token stored in the cookies with the one stored in the database. If the token is valid, the user is authenticated.

Managing Multiple Sessions 

The session management system enables WordPress to handle multiple login instances per user. For example, a user can stay logged in on different devices or browsers. If the token becomes invalid (e.g., due to expiration), the session is destroyed, forcing the user to log in again.

How Sessions Interact with User Data 

Sessions and user data are tightly integrated. When a user logs in: 

• Cookies are set: WordPress creates and stores the authentication and logged-in cookies. 

• Session tokens are validated: WordPress checks the token in the cookies against the stored session tokens in the wp_usermeta table. 

• User data is loaded: If the session is valid, WordPress loads user data from the wp_users table and merges it with capabilities from the wp_usermeta table, granting the user appropriate permissions. 

• Changes to user data: When a user makes changes (e.g., editing their profile), WordPress updates the relevant data in the database, but the session remains valid unless explicitly destroyed. 

This integration ensures that user data remains consistent across sessions, providing a seamless experience. 

Security Considerations and Best Practices 

Session and user data security is critical in WordPress, and several mechanisms help ensure the integrity and protection of this data: 

• Password Hashing: WordPress uses PHP’s password_hash() for password hashing, ensuring that passwords are stored securely. 

• Salts: WordPress salts authentication cookies with unique keys defined in the wp-config.php file, strengthening cookie security. 

• Use HTTPS: Always use HTTPS to secure cookies and prevent session hijacking via man-in-the-middle attacks. 

• Session Management Plugins: Plugins like Shield Security offer tools to audit and manage sessions, enhancing security. 

• Avoid Sensitive Data in Sessions: Sensitive user data should not be stored in sessions; instead, use encrypted user metadata when necessary. 

Common session-related issues include session hijacking (via stolen cookies) and session fixation (where an attacker tricks a user into using a specific session ID). WordPress mitigates these risks with features like IP and user-agent checks in session tokens.