Automatically Trash and Delete Polylang Translations When the Main Post Is Removed

Into the file functions.php of the current wp theme add php next code:

add_action('wp_trash_post', function ($post_id) {
    static $in_progress = false;
    if ($in_progress) { return; }
    $in_progress = true;

    if (!function_exists('pll_get_post_language') || !function_exists('pll_get_post_translations')) {
        $in_progress = false;
        return;
    }

    $post_lang = pll_get_post_language($post_id, 'slug');
    $default_lang = function_exists('pll_default_language') ? pll_default_language('slug') : pll_default_language();

    if ($post_lang && $default_lang && $post_lang === $default_lang) {
        $translations = pll_get_post_translations($post_id); // [ lang => post_id ]
        foreach ($translations as $lang => $tid) {
            if ((int)$tid === (int)$post_id) { continue; }

            if (get_post_status($tid) !== 'trash') {
                wp_trash_post($tid);
            }
        }
    }

    $in_progress = false;
}, 10, 1);

add_action('before_delete_post', function ($post_id) {
    static $in_progress = false;
    if ($in_progress) { return; }
    $in_progress = true;

    if (!function_exists('pll_get_post_language') || !function_exists('pll_get_post_translations')) {
        $in_progress = false;
        return;
    }

    $post_lang = pll_get_post_language($post_id, 'slug');
    $default_lang = function_exists('pll_default_language') ? pll_default_language('slug') : pll_default_language();

    if ($post_lang && $default_lang && $post_lang === $default_lang) {
        $translations = pll_get_post_translations($post_id);
        foreach ($translations as $lang => $tid) {
            if ((int)$tid === (int)$post_id) { continue; }

            if (get_post_status($tid) === 'trash') {
                wp_delete_post($tid, true);
            } else {
                wp_trash_post($tid);
                wp_delete_post($tid, true);
            }
        }
    }

    $in_progress = false;
}, 10, 1);