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wp_debug_mode()

This function’s access is marked private. This means it is not intended for use by plugin or theme developers, only in other core functions. It is listed here for completeness.

Set PHP error reporting based on WordPress debug settings.

Description

Uses three constants: WP_DEBUG, WP_DEBUG_DISPLAY, and WP_DEBUG_LOG. All three can be defined in wp-config.php. By default, WP_DEBUG and WP_DEBUG_LOG are set to false, and WP_DEBUG_DISPLAY is set to true.

When WP_DEBUG is true, all PHP notices are reported. WordPress will also display internal notices: when a deprecated WordPress function, function argument, or file is used. Deprecated code may be removed from a later version.

It is strongly recommended that plugin and theme developers use WP_DEBUG in their development environments.

WP_DEBUG_DISPLAY and WP_DEBUG_LOG perform no function unless WP_DEBUG is true.

When WP_DEBUG_DISPLAY is true, WordPress will force errors to be displayed. WP_DEBUG_DISPLAY defaults to true. Defining it as null prevents WordPress from changing the global configuration setting. Defining WP_DEBUG_DISPLAY as false will force errors to be hidden.

When WP_DEBUG_LOG is true, errors will be logged to wp-content/debug.log. When WP_DEBUG_LOG is a valid path, errors will be logged to the specified file.

Errors are never displayed for XML-RPC, REST, and Ajax requests.

Source

File: wp-includes/load.php 

function wp_debug_mode() {
	/**
	 * Filters whether to allow the debug mode check to occur.
	 *
	 * This filter runs before it can be used by plugins. It is designed for
	 * non-web run-times. Returning false causes the `WP_DEBUG` and related
	 * constants to not be checked and the default PHP values for errors
	 * will be used unless you take care to update them yourself.
	 *
	 * @since 4.6.0
	 *
	 * @param bool $enable_debug_mode Whether to enable debug mode checks to occur. Default true.
	 */
	if ( ! apply_filters( 'enable_wp_debug_mode_checks', true ) ) {
		return;
	}

	if ( WP_DEBUG ) {
		error_reporting( E_ALL );

		if ( WP_DEBUG_DISPLAY ) {
			ini_set( 'display_errors', 1 );
		} elseif ( null !== WP_DEBUG_DISPLAY ) {
			ini_set( 'display_errors', 0 );
		}

		if ( in_array( strtolower( (string) WP_DEBUG_LOG ), array( 'true', '1' ), true ) ) {
			$log_path = WP_CONTENT_DIR . '/debug.log';
		} elseif ( is_string( WP_DEBUG_LOG ) ) {
			$log_path = WP_DEBUG_LOG;
		} else {
			$log_path = false;
		}

		if ( $log_path ) {
			ini_set( 'log_errors', 1 );
			ini_set( 'error_log', $log_path );
		}
	} else {
		error_reporting( E_CORE_ERROR | E_CORE_WARNING | E_COMPILE_ERROR | E_ERROR | E_WARNING | E_PARSE | E_USER_ERROR | E_USER_WARNING | E_RECOVERABLE_ERROR );
	}

	if ( defined( 'XMLRPC_REQUEST' ) || defined( 'REST_REQUEST' ) || ( defined( 'WP_INSTALLING' ) && WP_INSTALLING ) || wp_doing_ajax() || wp_is_json_request() ) {
		ini_set( 'display_errors', 0 );
	}
}

Uses

Uses Description
wp-includes/load.php: wp_is_json_request()

Checks whether current request is a JSON request, or is expecting a JSON response.
wp-includes/load.php: wp_doing_ajax()

Determines whether the current request is a WordPress Ajax request.
wp-includes/load.php: enable_wp_debug_mode_checks

Filters whether to allow the debug mode check to occur.
wp-includes/plugin.php: apply_filters()

Calls the callback functions that have been added to a filter hook.

Changelog

Version Description
5.1.0 WP_DEBUG_LOG can be a file path.
3.0.0 Introduced.

© 2003–2019 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/functions/wp_debug_mode