How to query for pages/post depending on slug?

With a custom Page (post type page) and a custom Page Template, you can do it like so:

1. In the templates, make a new instance of WP_Query which is used for querying the posts in either the Romanian or English language.

2. In the query/function args for WP_Query and wp_get_archives(), use a custom parameter named lang which defines the language slug — ro for Romanian, en for English — and which is used to include only the posts or the archives having the posts where the post slug begins with <language slug>-, e.g. ro-.

The Code

1. The custom Page template:

   Note that I used the same code for both the Romanian and English versions, except that the lang is of course set to the corresponding language slug. If you want, you can use a custom meta data (e.g. _lang) for the Page and use just a single template for all languages, but you will need to implement that on your own.

   So on my test site, I’ve got these Pages:

   • RO Archive (/ro-archive/) using the template-ro-archive.php template

   • EN Archive (/en-archive/) using the template-en-archive.php template

   <?php
   // I'm only including the main content, but make sure your template contains
   // the Template Name header and the calls to get_header() and get_footer().
   ?>
   <ul>
       <?php wp_get_archives( [
           'lang' => 'ro',
       ] ); ?>
   </ul>
   
   <?php
   $paged = max( 1, get_query_var( 'paged' ) );
   
   // Query the posts.
   $query = new WP_Query( [
       'lang'           => 'ro',
       'paged'          => $paged,
       'posts_per_page' => 10,
   ] );
   
   // Display the loop.
   while ( $query->have_posts() ) :
       $query->the_post();
       // .. your code here.
   endwhile;
   
   // And a pagination.
   echo paginate_links( [
       'current' => $paged,
       'total'   => $query->max_num_pages,
   ] );
   
   // Lastly, restore the global $post variable.
   wp_reset_postdata();
   ?>
   

   And actually, you can also make the templates specific to the respective Page, e.g. use the name page-ro-archive.php and not template-ro-archive.php.

2. The query filter for WP_Query, using the posts_where hook:

   This code should go in the theme’s functions file.

   // Include only the posts where the slug begins with <language-slug>- like ro-
   add_filter( 'posts_where', function ( $where, $query ) {
       if ( ! is_admin() && $lang = $query->get( 'lang' ) ) {
           global $wpdb;
           $where .= $wpdb->prepare(
               " AND {$wpdb->posts}.post_name LIKE %s",
               $lang . '-%'
           );
       }
   
       return $where;
   }, 10, 2 );
   

3. The query filter for wp_get_archives(), using the getarchives_where hook:

   This code should go in the theme’s functions file.

   // Include only archives having posts where the slug begins with
   // <language-slug>- like ro-
   add_filter( 'getarchives_where', function ( $where, $parsed_args ) {
       if ( ! is_admin() && ! empty( $parsed_args['lang'] ) ) {
           global $wpdb;
           $where .= $wpdb->prepare(
               " AND post_name LIKE %s",
               $parsed_args['lang'] . '-%'
           );
       }
   
       return $where;
   }, 10, 2 );
   

Alternate Solution

Use a custom taxonomy, e.g. lang, for your articles/posts. That way, you could have the terms ro (Romanian) and en (English), then you’d have an archive at /lang/ro and /lang/en. And, you can have a single and standard template (i.e. taxonomy-lang.php) for those archives.

But,

1. You’ll need to assign all your articles to the correct lang term.
2. You’d still need to use the lang arg/filter for wp_get_archives().