WordPress获取某个标签关联的分类

反过来，我们可能会有这样的需求，既然可以获取某个分类的关联标签，那我能获取某个标签的关联分类吗？答案是可以的，将上面的代码稍微改一下就可以了：

function ludou_get_tag_categories($args) {

    global $wpdb;

    $categories = $wpdb->get_results

    ("

        SELECT DISTINCT terms1.term_id as cat_id

        FROM

            $wpdb->posts as p1

            LEFT JOIN $wpdb->term_relationships as r1 ON p1.ID = r1.object_ID

            LEFT JOIN $wpdb->term_taxonomy as t1 ON r1.term_taxonomy_id = t1.term_taxonomy_id

            LEFT JOIN $wpdb->terms as terms1 ON t1.term_id = terms1.term_id,

            $wpdb->posts as p2

            LEFT JOIN $wpdb->term_relationships as r2 ON p2.ID = r2.object_ID

            LEFT JOIN $wpdb->term_taxonomy as t2 ON r2.term_taxonomy_id = t2.term_taxonomy_id

            LEFT JOIN $wpdb->terms as terms2 ON t2.term_id = terms2.term_id

        WHERE

            t1.taxonomy = 'category' AND p1.post_status = 'publish' AND terms2.term_id IN (".$args['tags'].") AND

            t2.taxonomy = 'post_tag' AND p2.post_status = 'publish'

            AND p1.ID = p2.ID

        ORDER by cat_id

    ");

    $count = 0;

    if($categories) {

      foreach ($categories as $category) {

        $mycategory[$count] = get_term_by('id', $category->cat_id, 'category');

        $count++;

      }

    }

    else {

      $mycategory = NULL;

    }

    return $mycategory;

}

调用范例：

// 12,13是标签ID，多个用半角逗号隔开

$args = array( 'tags' => '12,13');

// 调用上面定义的函数，来获取ID为12，13的标签的关联分类

$categories = ludou_get_tag_categories($args);

// 输出我们获取到的关联分类，以列表形式打印

$content .= "<ul>";

if(!empty($categories)) {

  foreach ($categories as $category) {

    $content .= "<li><a href="".get_category_link( $category->term_id )."">".$category->name."</a></li>";

  }

}

$content .= "</ul>";

echo $content;