Table of Contents:
- What are constants and where are they set?
- Example of a simple constant definition:
- What are constants used for in WordPress?
- Database Configuration
- Security Improvement
- Debugging and Development
- Performance and Caching
- Automatic Updates and Installation
- How to Use Constants Properly?
- List of WordPress Constants
- Database Constants
- Security Constants
- Debugging and Development Constants
- Performance and Caching Constants
- File and Directory Constants
- Cron Job Constants
- Multisite Constants
- Update and Installation Constants
- REST API and XML-RPC Constants
- FTP/SSH Constants
- Conclusion
Last updated March 20th, 2025 01:54
WordPress is a very flexible platform, and one way to customize it to your needs is by using constants. Constants are fixed values that allow you to set various aspects of WordPress functionality, such as database connection, security, debugging, performance, updates, and more.
What are constants and where are they set?
Constants in WordPress are variables that cannot be changed after they are defined. In WordPress, constants are most commonly set in the wp-config.php file, which is located in the root directory of the installation.
Example of a simple constant definition:
define('WP_DEBUG', true);
This line enables the debug mode, which displays code errors and helps developers identify issues on the website.
What are constants used for in WordPress?
Database Configuration
During WordPress installation, important database connection constants such as DB_NAME, DB_USER, and DB_PASSWORD are set in the wp-config.php file. These constants determine which database WordPress will connect to.
Security Improvement
Some constants, such as DISALLOW_FILE_EDIT, prevent editing plugins and themes directly from the WordPress admin area, reducing the risk of hacker attacks. Constants like AUTH_KEY and SECURE_AUTH_KEY handle cookie encryption and secure logins.
Debugging and Development
Constants like WP_DEBUG, WP_DEBUG_LOG, and SAVEQUERIES help during development and testing by displaying errors, saving them to logs, or allowing you to track database queries.
Performance and Caching
Settings such as WP_CACHE, COMPRESS_CSS, and COMPRESS_SCRIPTS help speed up the website by enabling caching and file compression.
Automatic Updates and Installation
WP_AUTO_UPDATE_CORE controls automatic WordPress updates. Constants like DISALLOW_FILE_MODS can completely disable plugin installation and modifications, which is useful on websites where the administrator has limited management capabilities.
How to Use Constants Properly?
- Always define constants at the beginning of the wp-config.php file, at the latest before the line /* That’s all, stop editing! Happy publishing. */
- Avoid excessive use of debugging constants (WP_DEBUG, SAVEQUERIES) on production websites, as they can slow down performance.
- Be cautious about which constants and for what purpose you add to wp-config.php.
- Use comments and always carefully comment each constant you insert. This will make it easier for other website administrators or for yourself when reviewing the file after some time, especially when you forget the reason for many changes and modifications.
List of WordPress Constants
Database Constants
DB_NAME – The name of the database used for WordPress.
DB_USER – The username for database access.
DB_PASSWORD – The password for the database user.
DB_HOST – The database server address (e.g., localhost).
DB_CHARSET – The character set for the database (typically utf8).
DB_COLLATE – Character collation for the database (leave empty for default settings).
DB_PORT – The port for the database server (default is 3306).
DB_TABLE_PREFIX – Prefix for database tables (wp_, but can be changed for security).
Security Constants
AUTH_KEY, SECURE_AUTH_KEY, LOGGED_IN_KEY, NONCE_KEY – Security keys for authentication and cookie encryption.
AUTH_SALT, SECURE_AUTH_SALT, LOGGED_IN_SALT, NONCE_SALT – Additional salts to enhance encryption security.
FORCE_SSL_ADMIN – Forces HTTPS in the WordPress admin panel.
FORCE_SSL_LOGIN – Redirects login to HTTPS (deprecated, replaced by FORCE_SSL_ADMIN).
DISALLOW_UNFILTERED_HTML – Prevents admins from inserting dangerous HTML code (e.g., ).
WP_HTTP_BLOCK_EXTERNAL – Blocks all external HTTP requests unless allowed via WP_ACCESSIBLE_HOSTS.
WP_ACCESSIBLE_HOSTS – List of allowed external domains for HTTP requests.
ALLOW_UNFILTERED_UPLOADS – Allows uploading any file type (may be risky).
Debugging and Development Constants
WP_DEBUG – Enables debugging mode (displays PHP errors).
WP_DEBUG_LOG – Saves errors to a debug.log file in the /wp-content/ folder.
WP_DEBUG_DISPLAY – Determines if errors are shown directly on the page.
SCRIPT_DEBUG – Loads uncompressed versions of JavaScript and CSS files.
SAVEQUERIES – Logs all SQL queries and their execution times.
WP_ENVIRONMENT_TYPE – Specifies the environment type (local, development, staging, production).
WP_DISABLE_FATAL_ERROR_HANDLER – Disables the fatal error handler.
DIEONDBERROR – Displays database errors directly on the page.
Performance and Caching Constants
WP_MEMORY_LIMIT – The maximum amount of memory WordPress can use.
WP_MAX_MEMORY_LIMIT – Sets the maximum memory for scripts under heavy load.
WP_CACHE – Enables WordPress’s built-in caching.
COMPRESS_CSS – Enables CSS file compression.
COMPRESS_SCRIPTS – Enables JavaScript file compression.
ENFORCE_GZIP – Forces Gzip compression when sending content.
CONCATENATE_SCRIPTS – Combines JavaScript files into one for faster loading.
File and Directory Constants
WP_SITEURL – Sets the URL of the WordPress installation.
WP_HOME – Defines the home URL of the site.
WP_CONTENT_DIR – Absolute path to the wp-content directory.
WP_CONTENT_URL – URL of the wp-content folder.
UPLOADS – Sets a custom path for uploading files.
WP_PLUGIN_DIR – Absolute path to the plugins directory.
WP_PLUGIN_URL – URL to the plugins directory.
WPMU_PLUGIN_DIR – Path to Must-Use plugins (/wp-content/mu-plugins/).
WPMU_PLUGIN_URL – URL to Must-Use plugins.
Cron Job Constants
DISABLE_WP_CRON – Disables the built-in WP-Cron (useful with server-side cron jobs).
Multisite Constants
WP_ALLOW_MULTISITE – Enables the multisite network.
MULTISITE – Indicates if multisite is active.
SUBDOMAIN_INSTALL – Determines if multisite uses subdomains (true) or subdirectories (false).
DOMAIN_CURRENT_SITE – The main domain of the multisite network.
PATH_CURRENT_SITE – Path to the main site in the multisite network.
SITE_ID_CURRENT_SITE – ID of the main site in the multisite network.
BLOG_ID_CURRENT_SITE – ID of the main blog in the multisite network.
Update and Installation Constants
AUTOMATIC_UPDATER_DISABLED – Disables all automatic updates.
WP_AUTO_UPDATE_CORE – Sets whether the WordPress core updates automatically (true, false, minor).
DISALLOW_FILE_EDIT – Disables editing plugins and themes via the admin panel.
DISALLOW_FILE_MODS – Disables installing and updating plugins, themes, and core.
FS_METHOD – Determines the file system method for writing (direct, ssh2, ftpext, ftpsockets).
FS_CHMOD_FILE – Sets file permissions for new files.
FS_CHMOD_DIR – Sets directory permissions for new folders.
WP_ALLOW_REPAIR – Enables the repair of database tables (wp-admin/maint/repair.php).
REST API and XML-RPC Constants
WP_REST_DISABLED – Disables the REST API.
XMLRPC_REQUEST – Indicates that the page is being loaded via XML-RPC.
FTP/SSH Constants
FTP_HOST – The address of the FTP server for updates.
FTP_USER – The username for FTP access.
FTP_PASS – The password for the FTP user.
FTP_SSL – Enables SSL for FTP connection.
Conclusion
Using constants in WordPress is a crucial tool for anyone who wants full control over their website’s configuration. Whether it’s for debugging, security, performance, or managing updates, constants allow you to quickly customize WordPress to meet your specific needs. However, it’s essential to work with them carefully and ensure they are placed and used correctly in the wp-config.php file.
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