From 68af5620776be84e1f340727c1da44251fac219d Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov.ru@gmail.com>
Date: Tue, 22 Jun 2021 19:09:00 +0000
Subject: [PATCH] Code Modernization: Use a consistent check for parent items
 in `WP_Walker`.

This affects the `::walk()`, `::paged_walk()`, and `::get_number_of_root_elements()` methods.

PHP 8 changes the way string to number comparisons are performed: https://wiki.php.net/rfc/string_to_number_comparison

In particular, checking if an empty string is equal to zero in PHP 8 evaluates to `false`, not `true`.

For the `WP_Walker` class, this resulted in an incorrect handling of parent items in a few methods.

By explicitly checking for an `empty()` value instead, we make sure the check works as expected in PHP 8 and earlier versions.

Follow-up to [35876], [48960], [49043], [49076].

Props sunxiyuan, aristath, SergeyBiryukov.
Fixes #53474.
Built from https://develop.svn.wordpress.org/trunk@51204


git-svn-id: http://core.svn.wordpress.org/trunk@50813 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/class-wp-walker.php | 4 ++--
 wp-includes/version.php         | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/wp-includes/class-wp-walker.php b/wp-includes/class-wp-walker.php
index 13c0b23429..c76451cd94 100644
--- a/wp-includes/class-wp-walker.php
+++ b/wp-includes/class-wp-walker.php
@@ -342,7 +342,7 @@ class Walker {
 		$top_level_elements = array();
 		$children_elements  = array();
 		foreach ( $elements as $e ) {
-			if ( 0 == $e->$parent_field ) {
+			if ( empty( $e->$parent_field ) ) {
 				$top_level_elements[] = $e;
 			} else {
 				$children_elements[ $e->$parent_field ][] = $e;
@@ -412,7 +412,7 @@ class Walker {
 		$parent_field = $this->db_fields['parent'];
 
 		foreach ( $elements as $e ) {
-			if ( 0 == $e->$parent_field ) {
+			if ( empty( $e->$parent_field ) ) {
 				$num++;
 			}
 		}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 0bf23f7b33..7108295a72 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.8-beta2-51203';
+$wp_version = '5.8-beta2-51204';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.