<?php

/**

 * Error Protection API: WP_Fatal_Error_Handler class

 *

 * @package WordPress

 * @since   5.2.0

 */

/**

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

 *

 * 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.

 *

 * @since 5.2.0

 */

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'] ) && function_exists( 'load_default_textdomain' ) ) {

				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 ( ! class_exists( 'WP_Error' ) ) {

			require_once ABSPATH . WPINC . '/class-wp-error.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 );

	}

}