Undefined array key "QUERY_STRING" in _wp_get_site_editor_redirection_url()

[akshaydhere]

Got one Warning message in the Twenty Twenty-Five theme while opening in Appearance>Editor
WordPress Version - development version (6.8-RC2)
PHP Version - 8.2

Warning - Undefined array key "QUERY_STRING" in .../site-editor.php on line 34
Warning - Cannot modify header information- headers already sent by (output started at .../site-editor.php on line 34) in .../wp-admin/admin-header.php on line 14

[akshaydhere]

Warning message

[sainathpoojary]

Hey @akshaydhere,

Thank you for bringing up the issue. I attempted to replicate it but was unable to do so. I have attached a video referencing the steps I took.

Could you please check if I might be missing anything? Also, can you try testing it on a fresh WordPress installation?

Video: ​6.8.RC, ​6.9-alpha-60093-src

Environment

• WordPress: 6.8-RC2
• PHP: 8.2.27
• Server: nginx/1.16.0
• Database: mysqli (Server: 8.0.16 / Client: mysqlnd 8.2.27)
• Browser: Chrome 135.0.0.0
• OS: macOS
• Theme: Twenty Twenty-Five 1.1
• MU Plugins: None activated
• Plugins: Test Reports 1.2.0

[sabernhardt]

I did not find a way to receive the warning either, but I checked the history:

• [59794] added the _wp_get_site_editor_redirection_url() function.
• One of the commits in GB67199 ​changed the condition, removing isset() when it corrected QUERY_STRING.

[dilipbheda]

@sabernhardt @sainathpoojary We can fix this by using the empty() checker instead of !.

I've attached the patch for testing.

[tusharaddweb]

Test Summary:
A warning message was encountered while accessing the WordPress Site Editor under the Twenty Twenty-Five theme in WordPress version 6.8-RC2 with PHP 8.2.27. The issue was not reproducible in the local environment or WordPress Playground.

Test Environment:

WordPress Version: 6.8-RC2 (development version)

PHP Version: 8.2.27

Theme: Twenty Twenty-Five 1.1

Testing Environments:

Local WordPress installation

WordPress Playground

Steps to Reproduce:

Navigate to WordPress Admin Panel.

Go to Appearance > Editor.

Observe if any warnings or errors appear.

Observed Results:

Locally, no warning messages were observed.

In WordPress Playground, no warning messages were observed.

However, in a specific instance, the following warning appeared:

Warnings:

Warning: Undefined array key "QUERY_STRING" in .../site-editor.php on line 34

Warning: Cannot modify header information - headers already sent by (output started at .../site-editor.php on line 34) in .../wp-admin/admin-header.php on line 14

Expected Results:

The Site Editor should open without any warnings or errors.

Possible Causes & Analysis:

The issue might be environment-specific and could be triggered under certain server configurations.

The QUERY_STRING key might not always be set in the $_SERVER superglobal, leading to an undefined array key warning.

The warning output might cause early header output, leading to the headers already sent issue.

A recent change in WordPress 6.8-RC2 might be affecting this behavior.

Recommendations & Next Steps:

Debugging Approach:

Check $_SERVER contents before accessing QUERY_STRING.

Modify site-editor.php line 34 to ensure the key exists before usage:

$query_string = $_SERVERQUERY_STRING? ?? ;

Verify Reproducibility in Other Setups:

Test in a fresh WordPress installation with PHP 8.2.27.

Check if the issue persists across different hosting environments.

Report to WordPress Core Team:

If the issue is confirmed, report it as a bug in the WordPress Core Trac or GitHub.

Conclusion:
The issue was observed in a specific scenario but was not reproducible in all environments. Further investigation is needed to determine the root cause and provide a fix if necessary.

[johnbillion]

@tusharaddweb This slop is counter-productive. Please stop.

[rainynewt]

Test Summary:
A warning message was encountered while accessing the WordPress Site Editor under the Twenty Twenty-Five theme in WordPress version 6.8-RC2 with PHP 8.3.11.

Test Environment:

WordPress Version: 6.8-RC2 (development version)

PHP Version: 8.3.11

Theme: Twenty Twenty-Five 1.1

Testing Environments:

Local WordPress installation

WordPress Playground

Steps to Reproduce:

Navigate to WordPress Admin Panel.

Go to Appearance > Editor.

Observe if any warnings or errors appear.

Observed Results:

No errors or warnings were observed visually or in the debug.log. The issue might be observed in some specific environments, need info for replication of issue.

[shovan_jaya]

I have checked the issue about the Warning message in the Twenty Twenty-Five theme while opening in Appearance>Editor, But couldn't find any such issue in my local environment.

Environment

• WordPress: 6.8-RC2
• PHP: 8.2.27
• Server: nginx/1.26.1
• Database: mysqli (Server: 8.0.16 / Client: mysqlnd 8.2.27)
• Browser: Chrome 134.0.0.0
• OS: Linux
• Theme: Twenty Twenty-Five 1.1
• MU Plugins: None activated
• Plugins:
  • Test Reports 1.2.0

[sabernhardt]

cc: @youknowriad

[wildworks]

The environment in which I was able to reproduce this is ​Studio.

Presumably, whether $_SERVER['QUERY_STRING'] becomes undefined or an empty string when the query parameter is not present in the URL depends on the server type and settings.

However, I don't understand why this server variable is being checked in the first place. I read all the core ticket and Gutenberg PR related to this code, but I couldn't find out the reason.

In my opinion, this check should be able to be removed. Or is it a safeguard in case this internal function is called unintentionally from some special circumstances?

cc @joemcgill @Mamaduka @peterwilsoncc for visibility

[dilipbheda]

@wildworks I believe these changes were made two months ago in this [GitHub issue]​https://github.com/WordPress/wordpress-develop/issues/62585.

Ref: ​https://tinyurl.com/25lllqs5

I haven't reviewed the discussion in that ticket because I'm unable to access it.

[peterwilsoncc]

I've been able to reproduce this using Studio

I believe that it comes down to PHP configurations, $_SERVER['QUERY_STRING'] can either be an empty string or unset when the URL doesn't contain one.

Test Report

Description

This report validates whether the indicated patch works as expected.

Patch tested: 63224.patch​

Environment

• WordPress: 6.9-alpha-60132
• PHP: 8.2.10-dev
• Server: PHP.wasm
• Database: WP_SQLite_Translator (Server: 5.5 / Client: 3.40.1)
• Browser: Firefox 137.0
• OS: macOS
• Theme: Twenty Twenty-Five 1.1
• MU Plugins: None activated
• Plugins:
  • Test Reports 1.2.0

Actual Results

1. ✅ Issue resolved with patch.

Additional Notes

I've tested various redirects continue to work as expected. They do.

[peterwilsoncc]

In 60134:

Site Editor: Fix PHP warning in _wp_get_site_editor_redirection_url().

Fixes a PHP Warning for an undefined array key "QUERY_STRING" in _wp_get_site_editor_redirection_url() in some PHP configurations.

Depending on the configuration, $_SERVER['QUERY_STRING'] can either be unset or an empty string when no query string included in the URL. This changes the condition from a falsey check to an empty() check.

Props akshaydhere, dilipbheda, johnbillion, rainynewt, sabernhardt, sainathpoojary, shovan_jaya, tusharaddweb, wildworks.
Fixes #63224.

[peterwilsoncc]

Reopening for backport consideration of [60134] to the 6.8 branch, pending approval from another core committer.

[Mamaduka]

r60134 looks good to me for backporting. Thank you, @peterwilsoncc!

[zunaid321]

Reproduction Report

Description

This report validates whether the issue can be reproduced.

Environment

• WordPress: 6.8-RC2
• PHP: 8.2.10-dev
• Server: PHP.wasm
• Database: WP_SQLite_Translator (Server: 5.5 / Client: 3.40.1)
• Browser: Chrome 134.0.0.0
• OS: macOS
• Theme: Twenty Twenty-Five 1.1
• MU Plugins: None activated
• Plugins:
  • Test Reports 1.2.0

Actual Results

• Was NOT able to replicate the issue using WordPress Playground. ❌

Supplemental Artifacts

[peterwilsoncc]

In 60135:

Site Editor: Fix PHP warning in _wp_get_site_editor_redirection_url().

Fixes a PHP Warning for an undefined array key "QUERY_STRING" in _wp_get_site_editor_redirection_url() in some PHP configurations.

Depending on the configuration, $_SERVER['QUERY_STRING'] can either be unset or an empty string when no query string included in the URL. This changes the condition from a falsey check to an empty() check.

Reviewed by Mamaduka.
Merges [60134] to the 6.8 branch.

Props akshaydhere, dilipbheda, johnbillion, rainynewt, sabernhardt, sainathpoojary, shovan_jaya, tusharaddweb, wildworks.
Fixes #63224.