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