Playground is creating a fatal error in site health

[Zodiac1978]

Steps to reproduce:

1. Go to https://playground.wordpress.net/
2. Go to Tools -> Site Health (/wp-admin/site-health.php)
3. See the fatal error.

Here are the logs:

[13-Jun-2024 14:43:05 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function mysqli_get_client_info() in /wordpress/wp-admin/includes/class-wp-site-health.php:3
Stack trace:
#0 /wordpress/wp-admin/includes/class-wp-site-health.php(3): WP_Site_Health->get_test_utf8mb4_support()
#1 /wordpress/wp-admin/includes/class-wp-site-health.php(3): WP_Site_Health->perform_test(Array)
#2 /wordpress/wp-includes/class-wp-hook.php(3): WP_Site_Health->enqueue_scripts('site-health.php')
#3 /wordpress/wp-includes/class-wp-hook.php(3): WP_Hook->apply_filters(NULL, Array)
#4 /wordpress/wp-includes/plugin.php(2): WP_Hook->do_action(Array)
#5 /wordpress/wp-admin/admin-header.php(17): do_action('admin_enqueue_s...', 'site-health.php')
#6 /wordpress/wp-admin/site-health.php(2): require_once('/wordpress/wp-a...')
#7 {main}
  thrown in /wordpress/wp-admin/includes/class-wp-site-health.php on line 3
[13-Jun-2024 14:43:05 UTC] PHP Fatal: PHP.run() failed with exit code 255 and the following output:  PHPExecutionFailureError@https://playground.wordpress.net/worker-thread-492c00ae.js?wpVersion=6.5&phpVersion=8.0&php-extension=iconv&php-extension=mbstring&php-extension=xml-bundle&php-extension=gd&networking=no&storage=none&site-slug=wordpress:38:432
run@https://playground.wordpress.net/worker-thread-492c00ae.js?wpVersion=6.5&phpVersion=8.0&php-extension=iconv&php-extension=mbstring&php-extension=xml-bundle&php-extension=gd&networking=no&storage=none&site-slug=wordpress:53:1748
[13-Jun-2024 14:42:49 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function mysqli_get_client_info() in /wordpress/wp-admin/includes/class-wp-site-health.php:3
Stack trace:
#0 /wordpress/wp-admin/includes/class-wp-site-health.php(3): WP_Site_Health->get_test_utf8mb4_support()
#1 /wordpress/wp-admin/includes/class-wp-site-health.php(3): WP_Site_Health->perform_test(Array)
#2 /wordpress/wp-includes/class-wp-hook.php(3): WP_Site_Health->enqueue_scripts('site-health.php')
#3 /wordpress/wp-includes/class-wp-hook.php(3): WP_Hook->apply_filters(NULL, Array)
#4 /wordpress/wp-includes/plugin.php(2): WP_Hook->do_action(Array)
#5 /wordpress/wp-admin/admin-header.php(17): do_action('admin_enqueue_s...', 'site-health.php')
#6 /wordpress/wp-admin/site-health.php(2): require_once('/wordpress/wp-a...')
#7 {main}
  thrown in /wordpress/wp-admin/includes/class-wp-site-health.php on line 3
[13-Jun-2024 14:42:49 UTC] PHP Fatal: PHP.run() failed with exit code 255 and the following output:  PHPExecutionFailureError@https://playground.wordpress.net/worker-thread-492c00ae.js?wpVersion=6.5&phpVersion=8.0&php-extension=iconv&php-extension=mbstring&php-extension=xml-bundle&php-extension=gd&networking=no&storage=none&site-slug=wordpress:38:432
run@https://playground.wordpress.net/worker-thread-492c00ae.js?wpVersion=6.5&phpVersion=8.0&php-extension=iconv&php-extension=mbstring&php-extension=xml-bundle&php-extension=gd&networking=no&storage=none&site-slug=wordpress:53:1748

Not sure what is causing this ... but maybe it has to do with $wpdb->get_var( 'SELECT VERSION()' ); not working on SQLite.
https://github.com/WordPress/WordPress/blob/master/wp-admin/includes/class-wp-site-health.php#L212

We could polyfill this with a user defined function.
More ideas here: https://stackoverflow.com/questions/9646353/how-to-find-database-file-version

[Zodiac1978]

The function call to mysqli_get_client_info was used (until WordPress 6.5) in the method get_test_utf8mb4_support of the WP_Site_Health class. But in this class this method was removed for WordPress 6.6.
https://github.com/WordPress/WordPress/blob/master/wp-admin/includes/class-wp-site-health.php

Because WordPress 6.6 is not released yet, it is still shown in the documentation (just search for get_test_utf8mb4_support and you will find it):
https://developer.wordpress.org/reference/classes/wp_site_health/#source

This function was removed with this commit:
WordPress/WordPress@78d7296

Ticket: https://core.trac.wordpress.org/ticket/60096 (Milestone 6.6)
Changeset: https://core.trac.wordpress.org/changeset/57926

This explains why there is a fatal error. As mysqli_get_client_info does not work with a SQLite database.

Unsure how to proceed here. This function is already removed, so this fatal error will disappear with WordPress 6.6.

I don't know if this is something you want to backport. If yes, this would need a safeguard, to check if there is a MySQL/MariaDB or a SQLite database.

[Zodiac1978]

To prove my findings. Playground with WordPress 6.6 (beta 3 at the moment) is not having this error anymore:
https://playground.wordpress.net/?php=8.0&wp=beta&storage=none

[aristath]

Now that WP 6.6 has been released, I believe we can close this one 👍