WordPress进行二次开发的时候，需要调用WordPress网站某个分类下文章的关联标签，也就是该分类下各文章使用过的标签，今天就为大家分享一下WordPress调用分类关联的标签或者标签关联的分类方法。
实现代码：
在当前主题的functions.php文件中添加以下函数代码：
function ludou_get_category_tags($args) {
global $wpdb;
$tags = $wpdb->get_results
(\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”
SELECT DISTINCT terms2.term_id as tag_id, terms2.name as tag_name
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 $wpdb->terms as terms2 ON t2.term_id = terms2.term_id
WHERE
t1.taxonomy = \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’category\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’ AND p1.post_status = \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’publish\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’ AND terms1.term_id IN (\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”.$args[\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’categories\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’].\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”) AND
t2.taxonomy = \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’post_tag\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’ AND p2.post_status = \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’publish\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’
AND p1.ID = p2.ID
ORDER by tag_name
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”);
$count = 0;
if($tags) {
foreach ($tags as $tag) {
$mytag[$count] = get_term_by(\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’id\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’, $tag->tag_id, \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’post_tag\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’);
$count++;
}
}
else {
$mytag = NULL;
}
return $mytag;
}
然后在其他主题文件中，我们可以调用某个分类或某几个分类关联的标签：
// 12,13是分类ID，多个用半角逗号隔开
$args = array( \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’categories\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’ => \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’12,13\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\’);
// 调用上面定义的函数，来获取ID为12，13的分类的关联标签
$tags = ludou_get_category_tags($args);
// 输出我们获取到的关联标签，以列表形式打印
$content .= \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”<ul>\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”;
if(!empty($tags)) {
foreach ($tags as $tag) {
$content .= \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”<li><a href=\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”.get_tag_link($tag->term_id).\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”>\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”.$tag->name.\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”</a></li>\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”;
}
}
$content .= \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”</ul>\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\”;
echo $content;
好了，基本用法就这些，具体其他用法你可以自由地进行扩展。
获取某个标签关联的分类
反过来，我们可能会有这样的需求，既然可以获取某个分类的关联标签，那我能获取某个标签的关联分类吗？答案是可以的，将上面的代码稍微改一下就可以了，在当前主题的functions.php文件中添加以下函数代码：
function ludou_get_tag_categories($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：添加多个标签ID就调用多个标签的关联的分类
// 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;