WordPress Speed Up Service | WordPress Website Maintenance Packages I'm using plugins called Groups and Groups File Access to handle file downloads on my site. I'd like to use one of the methods defined in this plugin as an action hook. I've tried add_action( array( "Groups_File_Access", "groups_file_served" ), "my_custom_function" ) because the method is defined within a class, but this doesn't work. Is there a way to use an existing class method as a custom hook? I've seen many ways to hook a class method onto a native WP function, but not the other way around.