PHP Fatal error: Uncaught Error: Call to undefined function wp_json_decode()

Hi All,

I think I might have found a bug in the plugin’s code. When I installed it on my WP 6.6.1 instance running under PHP 8.3 and I tried to get a free license from the WP backend, the AJAX submission returned an error 500.

In the server logs, I found this error:

[...] request: "POST /wp-admin/admin-ajax.php HTTP/2.0", upstream: "fastcgi://unix:/run/php/php8.3-fpm.sock:", host: "[...]", referrer: "https://myhost/wp-admin/admin.php?page=newsletter_extensions_index"
2024/08/24 14:18:31 [error] 110651#110651: *171369 FastCGI sent in stderr: "PHP message: PHP Fatal error:  Uncaught Error: Call to undefined function wp_json_decode() in /[...]/wp-content/plugins/newsletter-extensions/plugin.php:71
Stack trace:
#0 /[...]/wp-includes/class-wp-hook.php(324): NewsletterExtensions->_register()
#1 /[...]/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()
#2 /[...]/wp-includes/plugin.php(517): WP_Hook->do_action()
#3 /[...]/wp-admin/admin-ajax.php(192): do_action()
#4 {main}
  thrown in /var/www/coramdeo.org.au/wp-content/plugins/newsletter-extensions/plugin.php on line 71"

The error is expected, since wp_json_decode() is not defined anywhere in the WP code:

root@frontend-1:~# grep -r wp_json_decode /[...]/

/[...]/wp-content/plugins/newsletter-extensions/plugin.php:        $data = wp_json_decode(wp_remote_retrieve_body($response));
root@frontend-1:~#

AFAIK, wp_json_decode() was deprecated and json_decode() should be used instead. I see that /plugins/newsletter-extensions/plugin.php contains a mix of both versions.

I replaced all instances of wp_json_decode() and wp_json_encode() in /plugins/newsletter-extensions/plugin.php with their newer equivalents and the free registration feature started working.

I would have normally opened a ticket to report this, but I can not open one unless I am a paying customer. Hope this helps.