WordPress 6.0 class-wp-widget.php fatal errors in PHP 8.1.6

Question

/wp-includes/class-wp-widget.php gives me an error for one blog, but not the other, and both have the same version of class-wp-widget.php which makes no sense to me.

PHP Fatal error: Uncaught ArgumentCountError: Too few arguments to function WP_Widget::__construct(), 0 passed in /home/www/stackexchange.com/wp-includes/class-wp-widget-factory.php on line 61 and at least 2 expected in /home/www/stackexchange.com/wp-includes/class-wp-widget.php:162

Reading the code, it appears class-wp-widget.php is the root of the problem, but I could be wrong.

My other (working) blog on the same server has this same file and I don't get the error.

You can see the broken WordPress function here https://developer.wordpress.org/reference/classes/wp_widget/__construct/

Is there a way to "turn off" widgets to deactivate this broken WordPress code?

Update: thanks @bosco for the idea, looking at the Stack trace helped...

Stack trace:
#0 /home/www/example.com/wp-includes/class-wp-widget-factory.php(61): WP_Widget->__construct()
#1 /home/www/example.com/wp-includes/widgets.php(115): WP_Widget_Factory->register()
#2 /home/www/example.com/wp-content/themes/theme1516/includes/register-widgets.php(22): register_widget()
#3 /home/www/example.com/wp-includes/class-wp-hook.php(307): load_my_widgets()
#4 /home/www/example.com/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters()
#5 /home/www/example.com/wp-includes/plugin.php(476): WP_Hook->do_action()
#6 /home/www/example.com/wp-includes/widgets.php(1854)

Since "register-widgets.php" is the only non-core code here, and because I assume @bosco's comment is correct, I commented out the old widgets and that at least removed the "white screen of death" meanwhile the homepage looks wonky, will probably just cut/paste the HTML from the PHP 7.x site.

Answer 1

In case you couldn’t revert to PHP older than 8.1 or fix the widget registration (and you trust your 10+ years old theme), you can update the line 61 of wp-includes/class-wp-widget-factory.php this way :

$this->widgets[ $widget ] = new $widget( $widget, $widget );

This may fix the widget registration.

Answer 2

I suspect the cause is a custom widget that has been built incorrectly. Take a look at this example from the Codex:

class My_Widget extends WP_Widget {

    /**
     * Sets up the widgets name etc
     */
    public function __construct() {
        $widget_ops = array( 
            'classname' => 'my_widget',
            'description' => 'My Widget is awesome',
        );
        parent::__construct( 'my_widget', 'My Widget', $widget_ops );
    }

What a lot of poorly built plugins do is this:

class My_Widget extends WP_Widget {

    /**
     * Sets up the widgets name etc
     */
    public function __construct() {
        parent::__construct();
    }

Or they fail to include a __construct method at all! Passing no parameters or not having a constructor is incorrect. Past versions of PHP may have substituted these values for null or undefined, resolving to ''`, but I would still have expected this to become a problem before upgrading to 8.1, and it would certainly have appeared in the error log as a notice.

So identify which plugin or theme is responsible for this, either with stack traces, or a process of elimination, perhaps even by doing a search of the codebase with a tool.

If this is in code that you maintain such as a custom theme or plugin, you can resolve the issue by implementing the Widget API correctly as the Codex and the devhub handbooks instruct. Specifically, by providing the first two parameters.

If you're not interested in fixing the widgets, you can also remove them from your site completely.

---

In the meantime, downgrade to 8.0 for a little while. Both 8.0 and 8.1 are currently supported versions of PHP and receiving updates. WordPress has yet to build official support for 8.0, and 8.1 is a very recent release ( early 2022 ), so it's unsurprising you encountered compatibility issues and clashes with 3rd party code when you upgraded.

Answer 3

For anyone still having this issue, you can try to go wordpress/wp-includes/class-wp-widget-factory.php on line 61 make this change to fix the issue without changing any other code:

Change this: $this->widgets[ $widget ] = new $widget();

To: $this->widgets[ $widget ] = new $widget( $widget, $widget );

Everything should work as expected now.