How to amend wordpress search so it queries taxonomy terms and category terms?

Question

I want to amend the search so if say I have taxonomy called \"author\" and add a term of \"Ian Rankin\" to a post, if I search for \"Ian Rankin\", I want that post to come up.

Answer 1

It could also be done by using MySQL's EXISTS function with a subquery that joins term_relationships with terms. I have created the following snippet and put it into functions.php:

// Search titles and tags
function and_extend_search( $search, &$wp_query ) {

    global $wpdb;

    if ( empty( $search ))
        return $search;

    $terms = $wp_query->query_vars[ 's' ];
    $exploded = explode( ' ', $terms );
    if( $exploded === FALSE || count( $exploded ) == 0 )
        $exploded = array( 0 => $terms );

    $search = '';

    foreach( $exploded as $tag ) {
        $search .= " AND (
            ($wpdb->posts.post_title LIKE '%$tag%')

            OR EXISTS
            (
                SELECT 
                    *
                FROM 
                    $wpdb->term_relationships 
                LEFT JOIN 
                    $wpdb->terms 
                ON 
                    $wpdb->term_relationships.term_taxonomy_id = $wpdb->terms.term_id
                WHERE
                        $wpdb->terms.name LIKE '%$tag%'
                    AND
                        $wpdb->term_relationships.object_id = $wpdb->posts.ID
            )
        )";
    }

    return $search;
}
add_filter('posts_search', 'and_extend_search', 500, 2);