[wp-trac] [WordPress Trac] #57469: retrieve_widgets(): fatal error when a sidebar's widgets set to null (array is expected) (was: Uncaught Error: array_merge(): Argument #3 must be of type array, null given in wp-includes/widgets.php on line 1342)

[WordPress Trac]

#57469: retrieve_widgets(): fatal error when a sidebar's widgets set to null (array
is expected)
--------------------------+---------------------
 Reporter:  kesselb       |       Owner:  (none)
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:
Component:  Widgets       |     Version:  4.9
 Severity:  normal        |  Resolution:
 Keywords:  php80 close   |     Focuses:
--------------------------+---------------------
Changes (by hellofromTonya):

 * keywords:  php8 has-patch has-unit-tests close => php80 close
 * version:   => 4.9


Old description:

> When changing from PHP 7.4 to PHP 8.0 it's not possible to activate our
> theme.
>

> Fatal error: Uncaught Error: array_merge(): Argument #3 must be of type
> array, null given in wp-includes/widgets.php on line 1342
>

> {{{
> array_merge()
> wp-includes/widgets.php:1342
>
> retrieve_widgets()
> wp-includes/widgets.php:1287
>
> _wp_sidebars_changed()
> wp-includes/class-wp-hook.php:310
>
> WP_Hook::apply_filters()
> wp-includes/class-wp-hook.php:332
>
> WP_Hook::do_action()
> wp-includes/plugin.php:517
>
> do_action()
> wp-includes/theme.php:3395
>
> check_theme_switched()
> wp-includes/class-wp-hook.php:308
>
> WP_Hook::apply_filters()
> wp-includes/class-wp-hook.php:332
>
> WP_Hook::do_action()
> wp-includes/plugin.php:517
>
> do_action()
> wp-settings.php:617
>
> require_once()
> wp-config.php:103
>
> require_once()
> wp-load.php:50
>
> require_once()
> wp-admin/admin.php:34
>
> require_once()
> wp-admin/plugins.php:10
> }}}
>

> Line 1342:
> {{{#!php
> <?php
>
> $shown_widgets = array_merge( ...array_values( $sidebars_widgets ) );
> }}}
>

> $sidebars_widgets
>

> {{{
> array (
>   'wp_inactive_widgets' =>
>   array (
>   ),
>   'sidebar-standard' =>
>   array (
>   ),
>   'sidebar-marken' => NULL,
>   'sidebar-typen' => NULL,
>   'sidebar-test' => NULL,
>   'sidebar-zubehoer' => NULL,
>   'sidebar-ratgeber' => NULL,
> )
> }}}
>

> PHP 8.0+ throws a type error when a non-array value is given to
> array_merge.
>
> I guess NULL is not a valid value for the sidebar widgets.
> Maybe our theme wrote this weird state to the options field.
>
> Patch: https://github.com/WordPress/wordpress-develop/pull/3848

New description:

 When changing from PHP 7.4 to PHP 8.0 it's not possible to activate our
 theme.

 {{{
 Fatal error: Uncaught Error: array_merge(): Argument #3 must be of type
 array, null given in wp-includes/widgets.php on line 1342
 }}}


 {{{
 array_merge()
 wp-includes/widgets.php:1342

 retrieve_widgets()
 wp-includes/widgets.php:1287

 _wp_sidebars_changed()
 wp-includes/class-wp-hook.php:310

 WP_Hook::apply_filters()
 wp-includes/class-wp-hook.php:332

 WP_Hook::do_action()
 wp-includes/plugin.php:517

 do_action()
 wp-includes/theme.php:3395

 check_theme_switched()
 wp-includes/class-wp-hook.php:308

 WP_Hook::apply_filters()
 wp-includes/class-wp-hook.php:332

 WP_Hook::do_action()
 wp-includes/plugin.php:517

 do_action()
 wp-settings.php:617

 require_once()
 wp-config.php:103

 require_once()
 wp-load.php:50

 require_once()
 wp-admin/admin.php:34

 require_once()
 wp-admin/plugins.php:10
 }}}


 Line 1342:
 {{{#!php
 <?php

 $shown_widgets = array_merge( ...array_values( $sidebars_widgets ) );
 }}}


 $sidebars_widgets


 {{{
 array (
   'wp_inactive_widgets' =>
   array (
   ),
   'sidebar-standard' =>
   array (
   ),
   'sidebar-marken' => NULL,
   'sidebar-typen' => NULL,
   'sidebar-test' => NULL,
   'sidebar-zubehoer' => NULL,
   'sidebar-ratgeber' => NULL,
 )
 }}}


 PHP 8.0+ throws a type error when a non-array value is given to
 array_merge.

 I guess NULL is not a valid value for the sidebar widgets.
 Maybe our theme wrote this weird state to the options field.

 Patch: https://github.com/WordPress/wordpress-develop/pull/3848

--

Comment:

 **Changes in the ticket:**
 * Updated the Summary to better reflect the issue being reported, i.e. for
 discoverability.
 * Updated the Version to 4.9.
 * Wrapped the PHP error in the Description.
 * Reset the keywords as the PR was closed.
 * Changed keyword to `php80` to identify which PHP version increased the
 error's severity.

 **Error across PHP versions:**
 If `null` or a non-array is set for the widgets of a sidebar, then PHP
 throws an error (see it in action https://3v4l.org/i45nZ):
 * < 7.3: `Warning: array_merge(): Argument #3 is not an array `
 * PHP 7.3 to 7.4: `Warning: array_merge(): Expected parameter 3 to be an
 array, null given`
 * PHP 8+: `Fatal error: Uncaught TypeError: array_merge(): Argument #3
 must be of type array, null given`.

 **Historical context:**

 * [41555] / #39693 (during WP 4.9):
    * Introduced `wp_map_sidebars_widgets()`.
    * `retrieve_widgets()`:
       * Invoked `wp_map_sidebars_widgets()` to map `$sidebars_widgets`
       * Added `$shown_widgets = call_user_func_array( 'array_merge',
 $sidebars_widgets );`.
 * [48839] / #50913 (during WP 5.6):
    * `retrieve_widgets()`: changed `call_user_func_array( 'array_merge',
 $sidebars_widgets );` to `array_merge( ...array_values( $sidebars_widgets
 ) );`.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/57469#comment:5>
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