Background of the issue:
I am experiencing issues on several websites after upgrading our servers from PHP 8.0.30 to 8.4.x, following WordPress's recommendations. The error logs are filled with 'Deprecated' notices, many of which seem to originate from Elementor Pro, WPML, Happy Addons, and WP Staging. The most common error is: Implicitly marking parameter ... as nullable is deprecated. Specific errors include: Deprecated: WPMLCoreComponentTranslationApplicationServiceLanguageService::setLanguageOfElement(): Implicitly marking parameter $sourceLanguageCode as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/wp-content/plugins/sitepress-multilingual-cms/vendor/wpml/wpml/src/Core/Component/Translation/Application/Service/LanguageService.php on line 32. I am following the documentation at https://make.wordpress.org/core/handbook/references/php-compatibility-and-wordpress-versions/.
Symptoms:
Display errors and 'Deprecated' notices after upgrading to PHP 8.4.x, specifically related to WPML and other plugins.
Questions:
Could you please recommend a solution for the deprecated errors?
Which stable PHP version should we use for full WPML compatibility?
