Bootstrap/Load: Ensure that the fatal error shutdown handler does not prevent other shutdown handlers from being called.

This changeset adds support for a new `wp_die()` argument `exit`, which defaults to true and determines whether `wp_die()` should actually terminate the request. The new fatal error handler then calls `wp_die()` with that argument set to false, as calling `die()` or `exit` from a PHP shutdown function prevents other shutdown functions from being called.

Props schlessera, johnbillion.
Fixes #46038. See #44458.

Built from https://develop.svn.wordpress.org/trunk@44671


git-svn-id: http://core.svn.wordpress.org/trunk@44502 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-shutdown-handler.php

@@ -136,7 +136,7 @@ class WP_Shutdown_Handler {
 			$php_error_pluggable = WP_CONTENT_DIR . '/php-error.php';
 			if ( is_readable( $php_error_pluggable ) ) {
 				require_once $php_error_pluggable;
-				die();
+				return;
 			}
 		}
 
@@ -166,7 +166,10 @@ class WP_Shutdown_Handler {
 
 		$message = __( 'The site is experiencing technical difficulties.' );
 
-		$args = array( 'response' => 500 );
+		$args = array(
+			'response' => 500,
+			'exit'     => false,
+		);
 		if ( function_exists( 'admin_url' ) ) {
 			$args['link_url']  = admin_url();
 			$args['link_text'] = __( 'Log into the admin backend to fix this.' );

wp-includes/functions.php

@@ -2957,6 +2957,7 @@ function wp_nonce_ays( $action ) {
  *                                  Default is the value of is_rtl().
  *     @type string $code           Error code to use. Default is 'wp_die', or the main error code if $message
  *                                  is a WP_Error.
+ *     @type bool   $exit           Whether to exit the process after completion. Default true.
  * }
  */
 function wp_die( $message = '', $title = '', $args = array() ) {
@@ -3201,7 +3202,9 @@ function _default_wp_die_handler( $message, $title = '', $args = array() ) {
 </body>
 </html>
 	<?php
-	die();
+	if ( $r['exit'] ) {
+		die();
+	}
 }
 
 /**
@@ -3236,7 +3239,9 @@ function _json_wp_die_handler( $message, $title = '', $args = array() ) {
 	}
 
 	echo wp_json_encode( $data );
-	die();
+	if ( $r['exit'] ) {
+		die();
+	}
 }
 
 /**
@@ -3262,7 +3267,9 @@ function _xmlrpc_wp_die_handler( $message, $title = '', $args = array() ) {
 		$error = new IXR_Error( $r['response'], $message );
 		$wp_xmlrpc_server->output( $error->getXml() );
 	}
-	die();
+	if ( $r['exit'] ) {
+		die();
+	}
 }
 
 /**
@@ -3291,9 +3298,16 @@ function _ajax_wp_die_handler( $message, $title = '', $args = array() ) {
 	}
 
 	if ( is_scalar( $message ) ) {
-		die( (string) $message );
+		$message = (string) $message;
+	} else {
+		$message = '0';
 	}
-	die( '0' );
+
+	if ( $r['exit'] ) {
+		die( $message );
+	}
+
+	echo $message;
 }
 
 /**
@@ -3302,15 +3316,26 @@ function _ajax_wp_die_handler( $message, $title = '', $args = array() ) {
  * This is the handler for wp_die when processing APP requests.
  *
  * @since 3.4.0
+ * @since 5.1.0 Added the $title and $args parameters.
  * @access private
  *
- * @param string $message Optional. Response to print. Default empty.
+ * @param string       $message Optional. Response to print. Default empty.
+ * @param string       $title   Optional. Error title (unused). Default empty.
+ * @param string|array $args    Optional. Arguments to control behavior. Default empty array.
  */
-function _scalar_wp_die_handler( $message = '' ) {
-	if ( is_scalar( $message ) ) {
-		die( (string) $message );
+function _scalar_wp_die_handler( $message = '', $title = '', $args = array() ) {
+	list( $message, $title, $r ) = _wp_die_process_input( $message, $title, $args );
+
+	if ( $r['exit'] ) {
+		if ( is_scalar( $message ) ) {
+			die( (string) $message );
+		}
+		die();
+	}
+
+	if ( is_scalar( $message ) ) {
+		echo (string) $message;
 	}
-	die();
 }
 
 /**
@@ -3328,6 +3353,7 @@ function _wp_die_process_input( $message, $title = '', $args = array() ) {
 	$defaults = array(
 		'response'          => 0,
 		'code'              => '',
+		'exit'              => true,
 		'back_link'         => false,
 		'link_url'          => '',
 		'link_text'         => '',

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-beta1-44670';
+$wp_version = '5.1-beta1-44671';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.