Fatal error: Uncaught Error: Call to a member function add_hooks() on array

Overview of the issue

When you upgrade WPML from the 3.9.1 version, you might encounter the following fatal error:

Fatal error: Uncaught Error: Call to a member function add_hooks() on array in ...\wp-content\plugins\sitepress-multilingual-cms\classes\action-filter-loader\class-wpml-action-filter-loader.php on line 52

 

Workaround

This issue happens if the “Core” plugin WPML Multilingual CMS is not updated first.

Please make sure that before updating WPML String Translation, WPML Translation Management or WPML Media Translation, you first update the WPML Multilingual CMS plugin.

If you are already facing this issue, you can try one of the following two things:

1. Install a backup of your site that was made prior to running into this issue. Then, upgrade your WPML plugins, making sure to first update the main WPML Multilingual CMS plugin first.
2. If you cannot perform the previously suggested step, then please try the following:
   • Access your site via FTP and rename the folders containing all WPML add-on plugins, like String Translation and Translation Management. Make sure not to rename the folder of the main WPML plugin (“sitepress-multilingual-cms”).
   • Update the WPML Multilingual CMS core plugin.
   • Rename the folders of WPML add-on plugins back to their initial estate.
   • Update all the WPML add-on plugins.