我正在尝试构建一个查询，以便按照日期自定义字段对一些帖子进行排序，其中日期的格式为dd/mm/yyyy。

它通过直接使用get_results 如本例所示：

$querystr = "
    SELECT *
    FROM wp_posts, wp_postmeta
    WHERE wp_posts.ID = wp_postmeta.post_id
    AND wp_postmeta.meta_key = \'my_cutom_date\'
    AND wp_posts.post_status = \'publish\'
    AND wp_posts.post_type = \'post\'
    ORDER BY STR_TO_DATE(wp_postmeta.meta_value, \'%d/%m/%Y\') ASC
";

但是，我想将这种行为转换为WP_Query, 使用posts_where 滤器我做到了这一点：

$args = array(
    \'post_type\' => \'post\',
    \'post_status\' => \'publish\',
    \'posts_per_page\' => 10,
    \'meta_key\' => \'my_custom_date\'
); 

function filter_orderby( $orderby = \'\' ) {  
    global $wpdb;
    $orderby .= " ORDER BY STR_TO_DATE($wpdb->postmeta.meta_value, \'%d/%m/%Y\') ASC ";
    return $orderby;
}

add_filter( \'posts_orderby\', \'filter_orderby\' );

但它似乎没有返回任何东西。我错过了什么？

function filter_orderby( $orderby ) {  
    global $wpdb;
    return " STR_TO_DATE({$wpdb->postmeta}.meta_value, \'%d/%m/%Y\') ASC ";
}