From 37f91b71c627a18c2cfff20fd50556d32b34a287 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov@git.wordpress.org>
Date: Wed, 27 Apr 2022 13:45:57 +0000
Subject: [PATCH] Bootstrap/Load: Avoid a PHP warning when setting the
 `$pagenow` global in `wp-includes/vars.php`.

In some scenarios where `is_admin()` returns true but `$_SERVER['PHP_SELF']` does not match a `wp-admin/*` location, setting the `$pagenow` global could trigger a PHP warning: `Undefined array key 1`.

This commit avoids the warning by checking whether the matches array is not empty.

Props janh2, konradyoast, peterwilsoncc.
Fixes #54700.

git-svn-id: https://develop.svn.wordpress.org/trunk@53294 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/vars.php | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/wp-includes/vars.php b/src/wp-includes/vars.php
index 5f9257e85a..e285ed8321 100644
--- a/src/wp-includes/vars.php
+++ b/src/wp-includes/vars.php
@@ -29,9 +29,11 @@ if ( is_admin() ) {
 	} else {
 		preg_match( '#/wp-admin/?(.*?)$#i', $_SERVER['PHP_SELF'], $self_matches );
 	}
-	$pagenow = $self_matches[1];
+
+	$pagenow = ! empty( $self_matches[1] ) ? $self_matches[1] : '';
 	$pagenow = trim( $pagenow, '/' );
 	$pagenow = preg_replace( '#\?.*?$#', '', $pagenow );
+
 	if ( '' === $pagenow || 'index' === $pagenow || 'index.php' === $pagenow ) {
 		$pagenow = 'index.php';
 	} else {