How to call a function or method that is Namespaced using another plugin
add_action‘s second parameter is a callable, it can accept a string (like what you did in the example) or an array of class-instance and function name. For example, if you want to call a method get_age() from Person class, you can do this: $person = new Person(); add_action( ‘hook_name’, array($person , ‘get_age’) );