Problem:
The user says that wpml_get_translated_slug hook always returns slut in default language.
Here's the code that the user uses:
echo apply_filters( 'wpml_get_translated_slug', get_post_field( 'post_name' ), 'page', 'en'); exit();
Solution:
In this case there was a misuse use of this hook.
The hook you are using (wpml_get_translated_slug) is intended to get the post-type slug translation in a specific language. But you are misusing it. You are trying to get the slug of a particular page of WordPress. A regular WordPress page doesn't have this "slug prefix" type. Its permalink consists only of the page slug itself.
Let's, for example, take a custom post type with the name of 'book'. In this case, the following will consist of the permalink.
post type slug = book
post slug = my-book
permalink = /book/my-book/
The wpml_get_translated_slug hook filters the /book/ part. WordPress's pages do not have this part.
Relevant Documentation:
https://wpml.org/wpml-hook/wpml_get_translated_slug/
