Get Taxonomy Terms By Other Taxonomy Term

getTaxTermsByOtherTaxTerm.php

<?php
function getTaxTermsByOtherTaxTerm($taxonomy_1, $term_id, $taxonomy_2, $post_type = NULL) {
    global $wpdb;
    $post_type_q = !empty($post_type_q) ? "AND p.post_type = '$post_type'" : "";
    $sql = "SELECT r.object_id FROM $wpdb->terms AS t
                INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id
                INNER JOIN $wpdb->term_relationships AS r ON r.term_taxonomy_id = tt.term_taxonomy_id
                INNER JOIN $wpdb->posts AS p ON (p.ID = r.object_id AND p.post_status = 'publish' $post_type_q)
                WHERE tt.taxonomy = '$taxonomy_1' AND t.term_id = $term_id";
    $res = $wpdb->get_col($sql);

    if ($res && count($res)) {
        $o_ids = implode(',', $res);
        $sql = "SELECT t.*, tt.* FROM $wpdb->terms AS t
                INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id
                INNER JOIN $wpdb->term_relationships AS r ON r.term_taxonomy_id = tt.term_taxonomy_id
                WHERE tt.taxonomy = '$taxonomy_2' AND r.object_id IN ($o_ids) GROUP BY t.term_id";

        $res = $wpdb->get_results($sql);
        var_dump($res);
        return $res;
    }
}

getTaxTermsByOtherTaxTerm('pa_color', 28, 'pa_country');