From e720a9ddc7ff7738584dc031e56727040dca0248 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov@git.wordpress.org>
Date: Thu, 28 Nov 2019 13:40:19 +0000
Subject: [PATCH] Date/Time: Make `get_permalink()` more resilient against PHP
 timezone changes.

Overriding default PHP timezone with `date_default_timezone_set()`, while not recommended, should not inadvertently result in changing existing permalinks.

Add a unit test.

Props Rarst, steevithak, archon810, maciejmackowiak, Ov3rfly, Cybr, hometowntrailers, scvleon, miette49.
Fixes #48623.

git-svn-id: https://develop.svn.wordpress.org/trunk@46795 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/link-template.php         | 15 +++++----
 tests/phpunit/tests/date/getPermalink.php | 39 +++++++++++++++++++++++
 2 files changed, 48 insertions(+), 6 deletions(-)
 create mode 100644 tests/phpunit/tests/date/getPermalink.php

diff --git a/src/wp-includes/link-template.php b/src/wp-includes/link-template.php
index 9419633632..5698ded47a 100644
--- a/src/wp-includes/link-template.php
+++ b/src/wp-includes/link-template.php
@@ -166,7 +166,6 @@ function get_permalink( $post = 0, $leavename = false ) {
 	$permalink = apply_filters( 'pre_post_link', $permalink, $post, $leavename );
 
 	if ( '' != $permalink && ! in_array( $post->post_status, array( 'draft', 'pending', 'auto-draft', 'future' ) ) ) {
-		$unixtime = strtotime( $post->post_date );
 
 		$category = '';
 		if ( strpos( $permalink, '%category%' ) !== false ) {
@@ -212,9 +211,11 @@ function get_permalink( $post = 0, $leavename = false ) {
 			$author     = $authordata->user_nicename;
 		}
 
-		$date           = explode( ' ', gmdate( 'Y m d H i s', $unixtime ) );
-		$rewritereplace =
-		array(
+		// This is not an API call because the permalink is based on the stored post_date value,
+		// which should be parsed as local time regardless of the default PHP timezone.
+		$date = explode( ' ', str_replace( array( '-', ':' ), ' ', $post->post_date ) );
+
+		$rewritereplace = array(
 			$date[0],
 			$date[1],
 			$date[2],
@@ -227,8 +228,10 @@ function get_permalink( $post = 0, $leavename = false ) {
 			$author,
 			$post->post_name,
 		);
-		$permalink      = home_url( str_replace( $rewritecode, $rewritereplace, $permalink ) );
-		$permalink      = user_trailingslashit( $permalink, 'single' );
+
+		$permalink = home_url( str_replace( $rewritecode, $rewritereplace, $permalink ) );
+		$permalink = user_trailingslashit( $permalink, 'single' );
+
 	} else { // if they're not using the fancy permalink option
 		$permalink = home_url( '?p=' . $post->ID );
 	}
diff --git a/tests/phpunit/tests/date/getPermalink.php b/tests/phpunit/tests/date/getPermalink.php
new file mode 100644
index 0000000000..0b6d86b13f
--- /dev/null
+++ b/tests/phpunit/tests/date/getPermalink.php
@@ -0,0 +1,39 @@
+<?php
+
+/**
+ * @group date
+ * @group datetime
+ * @group post
+ */
+class Tests_Date_Get_Permalink extends WP_UnitTestCase {
+
+	function tearDown() {
+		delete_option( 'permalink_structure' );
+		update_option( 'timezone_string', 'UTC' );
+		date_default_timezone_set( 'UTC' );
+
+		parent::tearDown();
+	}
+
+	/**
+	 * @ticket 48623
+	 */
+	public function test_should_return_correct_date_permalink_with_changed_time_zone() {
+		$timezone = 'America/Chicago';
+		update_option( 'timezone_string', $timezone );
+		update_option( 'permalink_structure', '/%year%/%monthnum%/%day%/%hour%/%minute%/%second%' );
+		date_default_timezone_set( 'UTC' );
+
+		$post_id = self::factory()->post->create(
+			array(
+				'post_date'     => '2018-07-22 21:13:23',
+				'post_date_gmt' => '2018-07-23 03:13:23',
+			)
+		);
+
+		$this->assertEquals( 'http://example.org/2018/07/22/21/13/23', get_permalink( $post_id ) );
+
+		date_default_timezone_set( $timezone );
+		$this->assertEquals( 'http://example.org/2018/07/22/21/13/23', get_permalink( $post_id ) );
+	}
+}