Site Editor: Browser reload causes PHP warning error on the Pages screen

[wildworks]

• Access Apperance > Editor > Pages > Select "Sample Page"
• The URL should be: ​http://localhost:8888/wp-admin/site-editor.php?p=%2Fpage&postId=2
• Reload your browser
• Confirm the PHP warning

Warning: Undefined variable $post in /var/www/html/wp-admin/site-editor.php on line 242

Warning: Attempt to read property "post_name" on null in /var/www/html/wp-admin/site-editor.php on line 242

Warning: Cannot modify header information - headers already sent by (output started at /var/www/html/wp-admin/site-editor.php:242) in /var/www/html/wp-admin/admin-header.php on line 14

This warning is new to 6.8.

[joemcgill]

Hi @wildworks, I'm not able to reproduce this in trunk nor in a fresh install of WP 6.8 beta 3. Is there any other information that would be needed to reproduce this issue? Do you have any other plugins active that could be triggering this error?

[websiteredev]

PHP error on mobile viewport

[websiteredev]

PHP error hidden on desktop

[websiteredev]

@joemcgill I'm able to reproduce it here with an install upgraded from 6.7.2 to 6.8 using the Beta Tester Plugin.

Environment

• WordPress: 6.8-beta3
• PHP: 8.3.11
• Server: nginx/1.26.1
• Database: mysqli (Server: 8.0.35 / Client: mysqlnd 8.3.11)
• Browser: Chrome 134.0.0.0
• OS: Windows 10/11
• Theme: Twenty Twenty-Three 1.6
• MU Plugins: None activated
• Plugins:
  • Health Check & Troubleshooting 1.7.1
  • Test Reports 1.2.0
  • WordPress Beta Tester 3.6.2
  • WP Activity Log 5.3.3

[wildworks]

PHP error hidden on desktop

Yes, the warning text may be hard to see in desktop view, but it is there.

[websiteredev]

Error on PHP 8.3.11

[websiteredev]

No error on PHP 7.4

[websiteredev]

Unable to reproduce on an identical site that is on PHP 7.4, maybe PHP version based? What PHP version are you on @wildworks ?

[wildworks]

I'm on PHP 8.2.27. Not tested on PHP 7.4.

[abcd95]

Hi @wildworks thanks for bringing this up.

After investigating the issue, I found the problem is in site-editor.php. When building the URL for template lookup, there's a variable naming inconsistency:

empty( $block_editor_context->post->post_name ) ? 'page' : 'page-' . $post->post_name,

The code correctly uses $block_editor_context->post in the first part, but then incorrectly uses $post in the second part. Since $post is undefined at this point, it triggers PHP warnings when the browser is reloaded.

The fix is to use the same variable throughout:

empty( $block_editor_context->post->post_name ) ? 'page' : 'page-' . $block_editor_context->post->post_name,

This resolves the warning in my testing. Let me know if this works for you and I can raise a PR with the fix.

[websiteredev]

@abcd95 This fixes the issue in my testing.

[narenin]

@wildworks I'm also able to reproduce it here with in the given environment.

Environment

WordPress: 6.8-beta3-60042-src
PHP: 8.3.11
Server: nginx/1.26.1
Database: mysqli (Server: 8.0.35 / Client: mysqlnd 8.3.11)
Browser: Chrome 134.0.0.0
OS: Windows 10/11
Theme: Twenty Twenty-Five 1.1
MU Plugins: None activated

Plugins:
Health Check & Troubleshooting 1.7.1

Test Reports 1.2.1

[narenin]

Screenshot of the error getting

[narenin]

Test Report :

Patch tested : ​https://github.com/WordPress/wordpress-develop/pull/8535

Environment

WordPress: 6.8-beta3-60042-src
PHP: 8.3.11
Server: nginx/1.26.1
Database: mysqli (Server: 8.0.35 / Client: mysqlnd 8.3.11)
Browser: Chrome 134.0.0.0
OS: Windows 10/11
Theme: Twenty Twenty-Five 1.1
MU Plugins: None activated

Plugins:
Health Check & Troubleshooting 1.7.1

Result:

After applying the patch the error has been gone.

Screenshot:

Thanks for the patch @himanshupathak95 !
This looks good to me, also with this patch the error/warning has been gone.

[wildworks]

@abcd95 Thanks for submitting the patch.

The code correctly uses $block_editor_context->post in the first part, but then incorrectly uses $post in the second part. Since $post is undefined at this point, it triggers PHP warnings when the browser is reloaded.

The fix is to use the same variable throughout:

This approach looks correct to me.

[soyebsalar]

Test Summary

This report verifies the resolution of a PHP warning in the WordPress Appearance Editor when accessing and reloading the Sample Page before and after applying the patch.
Test Environment

WordPress Version: 6.8 Beta 3
Server: Localhost (​http://localhost/)
PHP Version: 8.1
Browser: chrome, firefox mozilla

Test Steps and Results
Before Applying Patch

Navigate to Appearance > Editor.
Click on Pages and select Sample Page.
The URL should be:

​http://localhost/wp-admin/site-editor.php?p=%2Fpage&postId=2

Reload the browser.
Expected Result: The PHP warning should not appear.
Actual Result: The PHP warning appears.
Status: Failed.

After Applying Patch

Navigate to Appearance > Editor.
Click on Pages and select Sample Page.
Reload the browser.
Expected Result: No PHP warning should appear.
Actual Result: No PHP warning appears.
Status: Passed.

Conclusion

The applied patch successfully fixed the PHP warning in the WordPress 6.8 Beta 3 Appearance Editor. After applying the patch, reloading the Sample Page did not trigger any warnings.
Recommendation

Perform additional regression testing to ensure the patch does not introduce any unintended issues in other sections of the Appearance Editor.

[peterwilsoncc]

I've tested the ​associated pull request and validated the fix:

• warning no longer thrown on reload
• REST request for /wp/v2/templates/lookup?slug=page-sample-page is correctly preloaded on the branch and no longer made upon page load

This looks good for commit, thank you!

[peterwilsoncc]

In 60061:

Site Editor: Fix PHP warning pre-loading page REST requests.

Fix a PHP warning when opening a page directly in the site editor, eg by navigating to the URL /wp-admin/site-editor.php?p=%2Fpage&postId=200, caused by an undefined variable name.

Props abcd95, joemcgill, narenin, soyebsalar, websiteredev, wildworks.
Fixes #63122.