1<?php
  2/**
  3 * Error Protection API: WP_Fatal_Error_Handler class
  4 *
  5 * @package WordPress
  6 * @since 5.2.0
  7 */
  8
  9/**
 10 * Core class used as the default shutdown handler for fatal errors.
 11 *
 12 * A drop-in 'fatal-error-handler.php' can be used to override the instance of this class and use a custom
 13 * implementation for the fatal error handler that WordPress registers. The custom class should extend this class and
 14 * can override its methods individually as necessary. The file must return the instance of the class that should be
 15 * registered.
 16 *
 17 * @since 5.2.0
 18 */
 19#[AllowDynamicProperties]
 20class WP_Fatal_Error_Handler {
 21
 22	/**
 23	 * Runs the shutdown handler.
 24	 *
 25	 * This method is registered via `register_shutdown_function()`.
 26	 *
 27	 * @since 5.2.0
 28	 *
 29	 * @global WP_Locale $wp_locale WordPress date and time locale object.
 30	 */
 31	public function handle() {
 32		if ( defined( 'WP_SANDBOX_SCRAPING' ) && WP_SANDBOX_SCRAPING ) {
 33			return;
 34		}
 35
 36		// Do not trigger the fatal error handler while updates are being installed.
 37		if ( wp_is_maintenance_mode() ) {
 38			return;
 39		}
 40
 41		try {
 42			// Bail if no error found.
 43			$error = $this->detect_error();
 44			if ( ! $error ) {
 45				return;
 46			}
 47
 48			if ( ! isset( $GLOBALS['wp_locale'] ) && function_exists( 'load_default_textdomain' ) ) {
 49				load_default_textdomain();
 50			}
 51
 52			$handled = false;
 53
 54			if ( ! is_multisite() && wp_recovery_mode()->is_initialized() ) {
 55				$handled = wp_recovery_mode()->handle_error( $error );
 56			}
 57
 58			// Display the PHP error template if headers not sent.
 59			if ( is_admin() || ! headers_sent() ) {
 60				$this->display_error_template( $error, $handled );
 61			}
 62		} catch ( Exception $e ) {
 63			// Catch exceptions and remain silent.
 64		}
 65	}
 66
 67	/**
 68	 * Detects the error causing the crash if it should be handled.
 69	 *
 70	 * @since 5.2.0
 71	 *
 72	 * @return array|null Error information returned by `error_get_last()`, or null
 73	 *                    if none was recorded or the error should not be handled.
 74	 */
 75	protected function detect_error() {
 76		$error = error_get_last();
 77
 78		// No error, just skip the error handling code.
 79		if ( null === $error ) {
 80			return null;
 81		}
 82
 83		// Bail if this error should not be handled.
 84		if ( ! $this->should_handle_error( $error ) ) {
 85			return null;
 86		}
 87
 88		return $error;
 89	}
 90
 91	/**
 92	 * Determines whether we are dealing with an error that WordPress should handle
 93	 * in order to protect the admin backend against WSODs.
 94	 *
 95	 * @since 5.2.0
 96	 *
 97	 * @param array $error Error information retrieved from `error_get_last()`.
 98	 * @return bool Whether WordPress should handle this error.
 99	 */
100	protected function should_handle_error( $error ) {
101		$error_types_to_handle = array(
102			E_ERROR,
103			E_PARSE,
104			E_USER_ERROR,
105			E_COMPILE_ERROR,
106			E_RECOVERABLE_ERROR,
107		);
108
109		if ( isset( $error['type'] ) && in_array( $error['type'], $error_types_to_handle, true ) ) {
110			return true;
111		}
112
113		/**
114		 * Filters whether a given thrown error should be handled by the fatal error handler.
115		 *
116		 * This filter is only fired if the error is not already configured to be handled by WordPress core. As such,
117		 * it exclusively allows adding further rules for which errors should be handled, but not removing existing
118		 * ones.
119		 *
120		 * @since 5.2.0
121		 *
122		 * @param bool  $should_handle_error Whether the error should be handled by the fatal error handler.
123		 * @param array $error               Error information retrieved from `error_get_last()`.
124		 */
125		return (bool) apply_filters( 'wp_should_handle_php_error', false, $error );
126	}
127
128	/**
129	 * Displays the PHP error template and sends the HTTP status code, typically 500.
130	 *
131	 * A drop-in 'php-error.php' can be used as a custom template. This drop-in should control the HTTP status code and
132	 * print the HTML markup indicating that a PHP error occurred. Note that this drop-in may potentially be executed
133	 * very early in the WordPress bootstrap process, so any core functions used that are not part of
134	 * `wp-includes/load.php` should be checked for before being called.
135	 *
136	 * If no such drop-in is available, this will call {@see WP_Fatal_Error_Handler::display_default_error_template()}.
137	 *
138	 * @since 5.2.0
139	 * @since 5.3.0 The `$handled` parameter was added.
140	 *
141	 * @param array         $error   Error information retrieved from `error_get_last()`.
142	 * @param true|WP_Error $handled Whether Recovery Mode handled the fatal error.
143	 */
144	protected function display_error_template( $error, $handled ) {
145		if ( defined( 'WP_CONTENT_DIR' ) ) {
146			// Load custom PHP error template, if present.
147			$php_error_pluggable = WP_CONTENT_DIR . '/php-error.php';
148			if ( is_readable( $php_error_pluggable ) ) {
149				require_once $php_error_pluggable;
150
151				return;
152			}
153		}
154
155		// Otherwise, display the default error template.
156		$this->display_default_error_template( $error, $handled );
157	}
158
159	/**
160	 * Displays the default PHP error template.
161	 *
162	 * This method is called conditionally if no 'php-error.php' drop-in is available.
163	 *
164	 * It calls {@see wp_die()} with a message indicating that the site is experiencing technical difficulties and a
165	 * login link to the admin backend. The {@see 'wp_php_error_message'} and {@see 'wp_php_error_args'} filters can
166	 * be used to modify these parameters.
167	 *
168	 * @since 5.2.0
169	 * @since 5.3.0 The `$handled` parameter was added.
170	 *
171	 * @param array         $error   Error information retrieved from `error_get_last()`.
172	 * @param true|WP_Error $handled Whether Recovery Mode handled the fatal error.
173	 */
174	protected function display_default_error_template( $error, $handled ) {
175		if ( ! function_exists( '__' ) ) {
176			wp_load_translations_early();
177		}
178
179		if ( ! function_exists( 'wp_die' ) ) {
180			require_once ABSPATH . WPINC . '/functions.php';
181		}
182
183		if ( ! class_exists( 'WP_Error' ) ) {
184			require_once ABSPATH . WPINC . '/class-wp-error.php';
185		}
186
187		if ( true === $handled && wp_is_recovery_mode() ) {
188			$message = __( 'There has been a critical error on this website, putting it in recovery mode. Please check the Themes and Plugins screens for more details. If you just installed or updated a theme or plugin, check the relevant page for that first.' );
189		} elseif ( is_protected_endpoint() && wp_recovery_mode()->is_initialized() ) {
190			if ( is_multisite() ) {
191				$message = __( 'There has been a critical error on this website. Please reach out to your site administrator, and inform them of this error for further assistance.' );
192			} else {
193				$message = sprintf(
194					/* translators: %s: Support forums URL. */
195					__( 'There has been a critical error on this website. Please check your site admin email inbox for instructions. If you continue to have problems, please try the <a href="%s">support forums</a>.' ),
196					__( 'https://wordpress.org/support/forums/' )
197				);
198			}
199		} else {
200			$message = __( 'There has been a critical error on this website.' );
201		}
202
203		$message = sprintf(
204			'<p>%s</p><p><a href="%s">%s</a></p>',
205			$message,
206			/* translators: Documentation about troubleshooting. */
207			__( 'https://wordpress.org/documentation/article/faq-troubleshooting/' ),
208			__( 'Learn more about troubleshooting WordPress.' )
209		);
210
211		$args = array(
212			'response' => 500,
213			'exit'     => false,
214		);
215
216		/**
217		 * Filters the message that the default PHP error template displays.
218		 *
219		 * @since 5.2.0
220		 *
221		 * @param string $message HTML error message to display.
222		 * @param array  $error   Error information retrieved from `error_get_last()`.
223		 */
224		$message = apply_filters( 'wp_php_error_message', $message, $error );
225
226		/**
227		 * Filters the arguments passed to {@see wp_die()} for the default PHP error template.
228		 *
229		 * @since 5.2.0
230		 *
231		 * @param array $args Associative array of arguments passed to `wp_die()`. By default these contain a
232		 *                    'response' key, and optionally 'link_url' and 'link_text' keys.
233		 * @param array $error Error information retrieved from `error_get_last()`.
234		 */
235		$args = apply_filters( 'wp_php_error_args', $args, $error );
236
237		$wp_error = new WP_Error(
238			'internal_server_error',
239			$message,
240			array(
241				'error' => $error,
242			)
243		);
244
245		wp_die( $wp_error, '', $args );
246	}
247}
248