（most useful)搜索标题和字段一起 高级强大的搜索 全网唯一能用(更新版在后面)

// 在 functions.php 文件中添加以下代码

function custom_search_query( $query ) {
    if ( $query->is_search() && !is_admin() ) {
        // 获取搜索关键词
        $search_term = $query->query_vars['s'];

        // 设置 meta_query 以搜索元字段
        $meta_query = array(
            'relation' => 'OR',
            array(
                'key'     => '_oem_num', // 替换为您的元字段键
                'value'   => $search_term,
                'compare' => 'LIKE'
            ),
             array(
                'key'     => '_partnumber', // 替换为您的元字段键
                'value'   => $search_term,
                'compare' => 'LIKE'
            ),
        );

        // 将 meta_query 添加到查询中
        $query->set( 'meta_query', $meta_query );

        // 设置搜索关键词以搜索标题和内容
        $query->set( 's', $search_term ); // 保留搜索关键词
        $query->set( 'post_type', 'any' ); // 搜索所有类型的帖子
    }
    return $query;
}
add_filter( 'pre_get_posts', 'custom_search_query' );

// 添加自定义搜索条件
function custom_search_where( $where, $query ) {
    global $wpdb;

    if ( $query->is_search() && !is_admin() ) {
        $search_term = $query->query_vars['s'];
        $where .= " OR ({$wpdb->posts}.post_title LIKE '%" . esc_sql( $search_term ) . "%' ";
        $where .= " OR {$wpdb->posts}.post_content LIKE '%" . esc_sql( $search_term ) . "%' ";
        $where .= " OR EXISTS (SELECT * FROM {$wpdb->postmeta} WHERE {$wpdb->postmeta}.post_id = {$wpdb->posts}.ID AND {$wpdb->postmeta}.meta_value LIKE '%" . esc_sql( $search_term ) . "%'))";
    }

    return $where;
}
add_filter( 'posts_search', 'custom_search_where', 10, 2 );

上面 版本代码有个问题就是会搜索出媒体库的图片，文章类型是attachment, 这个文章类型是product的子级， 因为搜索的是产品上传的图片；还会搜索出 垃圾箱 trash 里面的帖子， 我们如何限制搜索的文章类型 是product , 又不会搜索出垃圾箱里的trash posts:

function custom_search_query( $query ) {
    if ( $query->is_search() && !is_admin() ) {
        // 获取搜索关键词
        $search_term = sanitize_text_field($query->query_vars['s']);

        // 设置 meta_query 以搜索元字段
        $meta_query = array(
            'relation' => 'OR',
            array(
                'key'     => 'oem_num', // 替换为您的元字段键
                'value'   => $search_term,
                'compare' => 'LIKE'
            ),
             array(
                'key'     => 'partnumber', // 替换为您的元字段键
                'value'   => $search_term,
                'compare' => 'LIKE'
            ),
        );

        // 将 meta_query 添加到查询中
        $query->set( 'meta_query', $meta_query );

        // 设置搜索关键词以搜索标题和内容
        $query->set( 's', $search_term ); // 保留搜索关键词
        $query->set( 'post_type', array('product') ); // 搜索所有类型的帖子
        $query->set( 'post_status', 'publish' );
        $query->set( 'post_parent', 0 );


    }
    return $query;
}
add_filter( 'pre_get_posts', 'custom_search_query' );

// 添加自定义搜索条件
function custom_search_where( $where, $query ) {
    global $wpdb;
    
    if ( $query->is_search() && !is_admin() ) {

        $search_term = $query->query_vars['s'];
         $where .= " AND {$wpdb->posts}.post_status = 'publish'";  // Only include published posts
        $where .= " AND {$wpdb->posts}.post_type = 'product'";  // Only search the 'product' post type
        $where .= " OR ({$wpdb->posts}.post_title LIKE '%" . esc_sql( $search_term ) . "%' ";
        $where .= " OR {$wpdb->posts}.post_content LIKE '%" . esc_sql( $search_term ) . "%' ";
        $where .= " OR EXISTS (SELECT * FROM {$wpdb->postmeta} WHERE {$wpdb->postmeta}.post_id = {$wpdb->posts}.ID AND {$wpdb->postmeta}.meta_value LIKE '%" . esc_sql( $search_term ) . "%'))";
        
    }

    return $where;
}
add_filter( 'posts_search', 'custom_search_where', 10, 2 );