WP_Fatal_Error_Handler

Core class used as the default shutdown handler for fatal errors.


Description Description

A drop-in ‘fatal-error-handler.php’ can be used to override the instance of this class and use a custom implementation for the fatal error handler that WordPress registers. The custom class should extend this class and can override its methods individually as necessary. The file must return the instance of the class that should be registered.


Source Source

File: wp-includes/class-wp-fatal-error-handler.php

class WP_Fatal_Error_Handler {

	/**
	 * Runs the shutdown handler.
	 *
	 * This method is registered via `register_shutdown_function()`.
	 *
	 * @since 5.2.0
	 */
	public function handle() {
		if ( defined( 'WP_SANDBOX_SCRAPING' ) && WP_SANDBOX_SCRAPING ) {
			return;
		}

		try {
			// Bail if no error found.
			$error = $this->detect_error();
			if ( ! $error ) {
				return;
			}

			if ( ! isset( $GLOBALS['wp_locale'] ) ) {
				load_default_textdomain();
			}

			if ( ! is_multisite() && wp_recovery_mode()->is_initialized() ) {
				wp_recovery_mode()->handle_error( $error );
			}

			// Display the PHP error template if headers not sent.
			if ( is_admin() || ! headers_sent() ) {
				$this->display_error_template( $error );
			}
		} catch ( Exception $e ) {
			// Catch exceptions and remain silent.
		}
	}

	/**
	 * Detects the error causing the crash if it should be handled.
	 *
	 * @since 5.2.0
	 *
	 * @return array|null Error that was triggered, or null if no error received or if the error should not be handled.
	 */
	protected function detect_error() {
		$error = error_get_last();

		// No error, just skip the error handling code.
		if ( null === $error ) {
			return null;
		}

		// Bail if this error should not be handled.
		if ( ! $this->should_handle_error( $error ) ) {
			return null;
		}

		return $error;
	}

	/**
	 * Determines whether we are dealing with an error that WordPress should handle
	 * in order to protect the admin backend against WSODs.
	 *
	 * @since 5.2.0
	 *
	 * @param array $error Error information retrieved from error_get_last().
	 * @return bool Whether WordPress should handle this error.
	 */
	protected function should_handle_error( $error ) {
		$error_types_to_handle = array(
			E_ERROR,
			E_PARSE,
			E_USER_ERROR,
			E_COMPILE_ERROR,
			E_RECOVERABLE_ERROR,
		);

		if ( isset( $error['type'] ) && in_array( $error['type'], $error_types_to_handle, true ) ) {
			return true;
		}

		/**
		 * Filters whether a given thrown error should be handled by the fatal error handler.
		 *
		 * This filter is only fired if the error is not already configured to be handled by WordPress core. As such,
		 * it exclusively allows adding further rules for which errors should be handled, but not removing existing
		 * ones.
		 *
		 * @since 5.2.0
		 *
		 * @param bool  $should_handle_error Whether the error should be handled by the fatal error handler.
		 * @param array $error               Error information retrieved from error_get_last().
		 */
		return (bool) apply_filters( 'wp_should_handle_php_error', false, $error );
	}

	/**
	 * Displays the PHP error template and sends the HTTP status code, typically 500.
	 *
	 * A drop-in 'php-error.php' can be used as a custom template. This drop-in should control the HTTP status code and
	 * print the HTML markup indicating that a PHP error occurred. Note that this drop-in may potentially be executed
	 * very early in the WordPress bootstrap process, so any core functions used that are not part of
	 * `wp-includes/load.php` should be checked for before being called.
	 *
	 * If no such drop-in is available, this will call {@see WP_Fatal_Error_Handler::display_default_error_template()}.
	 *
	 * @since 5.2.0
	 *
	 * @param array $error Error information retrieved from `error_get_last()`.
	 */
	protected function display_error_template( $error ) {
		if ( defined( 'WP_CONTENT_DIR' ) ) {
			// Load custom PHP error template, if present.
			$php_error_pluggable = WP_CONTENT_DIR . '/php-error.php';
			if ( is_readable( $php_error_pluggable ) ) {
				require_once $php_error_pluggable;

				return;
			}
		}

		// Otherwise, display the default error template.
		$this->display_default_error_template( $error );
	}

	/**
	 * Displays the default PHP error template.
	 *
	 * This method is called conditionally if no 'php-error.php' drop-in is available.
	 *
	 * It calls {@see wp_die()} with a message indicating that the site is experiencing technical difficulties and a
	 * login link to the admin backend. The {@see 'wp_php_error_message'} and {@see 'wp_php_error_args'} filters can
	 * be used to modify these parameters.
	 *
	 * @since 5.2.0
	 *
	 * @param array $error Error information retrieved from `error_get_last()`.
	 */
	protected function display_default_error_template( $error ) {
		if ( ! function_exists( '__' ) ) {
			wp_load_translations_early();
		}

		if ( ! function_exists( 'wp_die' ) ) {
			require_once ABSPATH . WPINC . '/functions.php';
		}

		if ( is_protected_endpoint() ) {
			$message = __( 'The site is experiencing technical difficulties. Please check your site admin email inbox for instructions.' );
		} else {
			$message = __( 'The site is experiencing technical difficulties.' );
		}

		$args = array(
			'response' => 500,
			'exit'     => false,
		);

		/**
		 * Filters the message that the default PHP error template displays.
		 *
		 * @since 5.2.0
		 *
		 * @param string $message HTML error message to display.
		 * @param array  $error   Error information retrieved from `error_get_last()`.
		 */
		$message = apply_filters( 'wp_php_error_message', $message, $error );

		/**
		 * Filters the arguments passed to {@see wp_die()} for the default PHP error template.
		 *
		 * @since 5.2.0
		 *
		 * @param array $args Associative array of arguments passed to `wp_die()`. By default these contain a
		 *                    'response' key, and optionally 'link_url' and 'link_text' keys.
		 * @param array $error Error information retrieved from `error_get_last()`.
		 */
		$args = apply_filters( 'wp_php_error_args', $args, $error );

		$wp_error = new WP_Error(
			'internal_server_error',
			$message,
			array(
				'error' => $error,
			)
		);

		wp_die( $wp_error, '', $args );
	}
}

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Version Description
5.2.0 Introduced.

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