Get the original language post ID for WPML-translated posts

Problem:

You have a post that has been translated into multiple languages using WPML.
You want to find out the ID of the original post, i.e. the equivalent post in the source langugae.

Solution:

As far as I know, there is no WPML API for this. You can, however, use $wpdb in order to query the database directly.

Here’s the SQL statement:

SELECT trans2.element_id
FROM wp_icl_translations AS trans1
INNER JOIN wp_icl_translations AS trans2
ON trans2.trid = trans1.trid
WHERE trans1.element_id = #myid#
AND trans2.source_language_code IS NULLs

where #myid# is the ID of your current (possibly translated) post.

The algorithm works like this:

1. Find out the  translation ID (column trid) for the current post by selecting the row for the given post ID (column element_id)
2. Find all rows with the same translation ID
3. Select only the row where the source language is NULL – this is the original post.

You can use it like this:

global $wpdb;
$orig_lang_id = $wpdb->get_var("SELECT trans2.element_id FROM wp_icl_translations AS trans1 INNER JOIN wp_icl_translations AS trans2 ON trans2.trid = trans1.trid WHERE trans1.element_id = ".get_the_ID()." AND trans2.source_language_code IS NULL");

and then use $orig_lang_id where required. Note that $orig_lang_id is NULL if the query fails. The main reason for the query to fail is if there is no entry for the given post ID in the wp_icl_translations table.

If the current post is the source post, $orig_lang_id is the same as get_the_ID(), i.e. the current ID of the post.

In my test, the code still works (i.e. returns the correct post ID) even when creating brand-new entry without any translations being present.