Uncaught TypeError: method_exists() […] in widget-conditions.php

Hi all,

I’ve done a quick search here on these forums, and, although a lot of Uncaught TypeErrors have been reported, this seems to be a ‘new’ one — at least, as far as I could search. It’s also quite easy to fix.

I’m on Ubuntu 20.04.2 LTS, running nginx/1.19.6 with PHP 8.0.2 (provided via php-fpm), WordPress 5.6.1 and Jetpack 9.4. My configuration is rather a complex one (many things can go wrong), but this time I can trace it down to Jetpack. The following error is thrown when saving a (Jetpack) widget (after adding it):

2021/02/07 15:50:04 [error] 3799479#3799479: *372 FastCGI sent in stderr: "PHP message: PHP Fatal error:  Uncaught TypeError: method_exists(): Argument #1 ($object_or_class) must be of type object|string, null given in <WP_PATH>/wp-content/plugins/jetpack/modules/widget-visibility/widget-conditions.php:27

(path redacted)

The culprit, around line 27, is the following bit of code:

                // TODO: Replace ‛$current_screen->is_block_editor()‛ with ‛wp_should_load_block_editor_scripts_and_styles()‛ that is introduced in WP 5.6
                if ( method_exists( $current_screen, 'is_block_editor' ) && $current_screen->is_block_editor() ) {

Under PHP 7.X, if $current_screen was null, this would throw a warning or a notice, but PHP 8.X, as we all know, is so much stricter, and since you cannot apply method_exists() to a null object — it throws a fatal error. The consequence is that the widget never gets saved and/or added to a sidebar.

A trivial, quick & dirty fix is simply to check if $current_screen is empty, e.g.:

if ( ! empty( $current_screen ) && method_exists( $current_screen, 'is_block_editor' ) && $current_screen->is_block_editor() ) {

That should make PHP 8.0 happy.

Note that the comment before that line implies that this particular bit of code will be replaced by a different function; as such, I’d imagine that future versions of Jetpack will change the way this works.

In the meantime — unless Automattic releases a quick & dirty patch first! — now you know what to do to keep WordPress happy 🙂

P.S. There are other, similar annoyances when using PHP 8.0, but fortunately, most just fill the logs with warnings, not fatal errors.

• This topic was modified 3 years, 6 months ago by Gwyneth Llewelyn. Reason: Fixed backticks-inside-backticks issue, which made the comment unreadable