WordPress でユーザー名とか、タグ名・カテゴリ名も検索対象に

wp-custom-search.php

<?php
function custom_search($search, $wp_query) {
	global $wpdb;

	//サーチページ以外だったら終了
	if (!$wp_query->is_search)
		return $search;
	if (!isset($wp_query->query_vars))
		return $search;

	// ユーザー名とか、タグ名・カテゴリ名も検索対象に
	$search_words = explode(' ', isset($wp_query->query_vars['s']) ? $wp_query->query_vars['s'] : '');
	if ( count($search_words) > 0 ) {
		$search = '';
		foreach ( $search_words as $word ) {
			if ( !empty($word) ) {
				$search_word = $wpdb->escape("%{$word}%");
				$search .= " AND (
 {$wpdb->posts}.post_title LIKE '{$search_word}'
 OR {$wpdb->posts}.post_content LIKE '{$search_word}'
 OR {$wpdb->posts}.post_author IN (
   SELECT distinct ID
   FROM {$wpdb->users}
   WHERE display_name LIKE '{$search_word}'
   )
 OR {$wpdb->posts}.ID IN (
   SELECT distinct r.object_id
   FROM {$wpdb->term_relationships} AS r
   INNER JOIN {$wpdb->term_taxonomy} AS tt ON r.term_taxonomy_id = tt.term_taxonomy_id
   INNER JOIN {$wpdb->terms} AS t ON tt.term_id = t.term_id
   WHERE t.name LIKE '{$search_word}'
     OR t.slug LIKE '{$search_word}'
     OR tt.description LIKE '{$search_word}'
   )
) ";
			}
		}
	}

	return $search;
}
add_filter('posts_search','custom_search', 10, 2);