deprecated message using default wp theme 20-13

[neo2k23]

I get a deprecated message on using a default wp theme 20-13

$title_array = apply_filters( 'wp_title_parts', explode( $t_sep, $title ) );

<b>Deprecated</b>:  explode(): Passing null to parameter #2 ($string) of type string is deprecated in <b>/home/public_html/wp-includes/general-template.php</b> on line <b>1441</b><br />
Default theme | Een andere Demo Blog websites site</title>

apparently when line 1439 is reached $title is and can be empty.

changing the code to

	if ( !empty( $title ) )  $title_array = apply_filters( 'wp_title_parts', explode( $t_sep, $title ) );
	else $title_array  = array();

fixes the issue. Please adapt. Thank you

[neo2k23]

line 1441 should be 1439. I already change to the new code and reverted back leaving to empty lines just to regenerate the message for posting this issue. Apologies for this mistake. The correct linenumber that generates the issue in the unmodified file is 1439

[audrasjb]

Hello and thanks for the report.
Could you please share the steps to help reproduce the deprecated message?
Thanks

[neo2k23]

@audrasjb

I have debug mode enabled, using a multisite with using php 8.2.28 and activate the default wp 20-13 theme and view the home page. In the browser title tab just before the correct title you see the deprecated message.

if i enable tracking i get this

	[22-Apr-2025 12:46:53 UTC] PHP Deprecated:  explode(): Passing null to parameter #2 ($string) of type string is deprecated in /home/public_html/wp-includes/general-template.php on line 1439
	[22-Apr-2025 12:46:53 UTC] Array
	(
		[0] => Array
			(
				[file] => /home/public_html/wp-content/themes/twentythirteen/header.php
				[line] => 16
				[function] => wp_title
			)

		[1] => Array
			(
				[file] => /home/public_html/wp-includes/template.php
				[line] => 810
				[args] => Array
					(
						[0] => /home/public_html/wp-content/themes/twentythirteen/header.php
					)

				[function] => require_once
			)

		[2] => Array
			(
				[file] => /home/public_html/wp-includes/template.php
				[line] => 745
				[function] => load_template
			)

		[3] => Array
			(
				[file] => /home/public_html/wp-includes/general-template.php
				[line] => 48
				[function] => locate_template
			)

		[4] => Array
			(
				[file] => /home/public_html/wp-content/themes/twentythirteen/index.php
				[line] => 17
				[function] => get_header
			)

		[5] => Array
			(
				[file] => /home/public_html/wp-includes/template-loader.php
				[line] => 106
				[args] => Array
					(
						[0] => /home/public_html/wp-content/themes/twentythirteen/index.php
					)

				[function] => include
			)

		[6] => Array
			(
				[file] => /home/public_html/wp-blog-header.php
				[line] => 19
				[args] => Array
					(
						[0] => /home/public_html/wp-includes/template-loader.php
					)

				[function] => require_once
			)

		[7] => Array
			(
				[file] => /home/public_html/index.php
				[line] => 17
				[args] => Array
					(
						[0] => /home/public_html/wp-blog-header.php
					)

				[function] => require
			)

	)

[SirLouen]

Reproduction Report

Description

This report can't validate that the issue can be reproduced.

Environment

• WordPress: 6.8
• PHP: 8.2.10-dev
• Server: PHP.wasm
• Database: WP_SQLite_Translator (Server: 5.5 / Client: 3.40.1)
• Browser: Chrome 135.0.0.0
• OS: Windows 10/11
• Theme: Twenty Thirteen 4.4
• MU Plugins: None activated
• Plugins:
  • Test Reports 1.2.0
  • WP Debugging 2.12.2

Reproduction Steps

1. Create a new ​Playground with PHP 8.2 and Twentythirteen
2. Enable WP Debugging plugin full
3. Check homepage
4. ❌ No deprecation errors

Actual Results

1. ❌ Can't reproduce the deprecation notice

Additional Notes

@neo2k23
Please check the ​WP Playground and see if you can reproduce this by yourself. This is a clean, brand-new WordPress environment to test this kind of thing. When we cannot reproduce things, we assume that the problem relies on the user's host settings typically (or a WP different version, although you have a couple of versions to check there).

Question: Have you done some sort of special edit to the template, that removes head title or something? I've also tried removing title and subtitles in General, but still, I can't get that error.

[neo2k23]

i did not edit or change any code. i just turned on by accident the default 20-13 theme and got the error.

I just tested this in my local host server and it does not happen. I guess its somehow related to the multisite which is a old one (2012).

Please close the issue. Sorry for this i should have tested this on my local server first.

[SirLouen]

Ok, thanks for the prompt response. Closing.

[neo2k23]

@SirLouen @audrasjb

I can consistenty recreate the issue in ​https://playground.wordpress.net/?php=8.2&wp=6.8&networking=yes&language=&multisite=no&random=30295bbjxfg

create a static page called blog and set that page as your blog page in the wp reading settings

Make sure the home page is set to -- select -- in the wp reading settings.

Now view thefront of the website. The browser tab now has the issue and shows first the deprecated message.

​https://share.zight.com/d5ukE8XA

[SirLouen]

Got it.

[sabernhardt]

The deprecation notice is already reported on #61352, if you would like to follow that.

The message can display with any theme from Twenty Ten to Twenty Fourteen—and probably many more of the ​directory themes that use the wp_title function.