WordPress has specific debugging systems to standardize code throughout the core, plugins, and themes. There are several WordPress debugging tools, so we will explain how we can make use of them.

A PHP constant that, when set to true, activates "debugging" mode in WordPress. Its default value is false, and the recommended file to set its value is wp-config.php in one of the following ways:

define('WP_DEBUG', true);
define('WP_DEBUG', false);

With this tool, we will be able to see the most general errors in WordPress.

Complements the WP_DEBUG mode, causing all errors to also be saved to a debug.log log file within the /wp-content/ directory. This is useful when you want to review all notifications later or need to see notifications generated in delay (e.g. during an AJAX request or wp-cron execution).

define('WP_DEBUG_LOG', true);
​

Complements the WP_DEBUG mode that controls whether debugging messages are displayed within HTML pages or not. By default, it is 'true,' which shows errors and warnings as they are generated. Setting this to false will hide all errors. It should be used in conjunction with WP_DEBUG_LOG so that errors can be reviewed later.

define('WP_DEBUG_DISPLAY', false);
​

A related constant that will force WordPress to use the "dev" versions of core CSS and Javascript files instead of the minified versions that are normally loaded. This is useful when you are checking modifications for any .js or .css internal file.

define('SCRIPT_DEBUG', true);

The SAVEQUERIES definition saves database queries in an array, and that array can be displayed to help analyze such queries.

The array is stored in the global $wpdb->queries.

Example code, insert it into your wp-config.php file, will record all errors, news, and warnings to a file named debug.log in the wp-content directory. It will also hide errors so that they do not interrupt page generation.

// Activate WP_DEBUG mode
define('WP_DEBUG', true);
​
// Activate debugging log to /wp-content/debug.log file
define('WP_DEBUG_LOG', true);
​
// Disable display of errors and warnings
define('WP_DEBUG_DISPLAY', false);
@ini_set('display_errors',0);
​
// Use dev versions of core JS and CSS files (only needed if you are modifying those core files)
define('SCRIPT_DEBUG', true);
​

Within the WordPress module library, we have a plugin that can allow us to identify any type of error on our website. Also, through this plugin, it is possible to debug the speed of our website, knowing which plugins may be overloading our website.