Wordpress删除文章同时删除图片

WordPress怎样实行删掉文章时一起删除图片包括的附件,将代码加入到：functions.php.

//删除文章时删除图片附件开始
function delete_post_and_attachments($post_ID) {
    global $wpdb;
    //删除特色图片
    $thumbnails = $wpdb->get_results( "SELECT * FROM $wpdb->postmeta WHERE meta_key = '_thumbnail_id' AND post_id = $post_ID" );
    foreach ( $thumbnails as $thumbnail ) {
        wp_delete_attachment( $thumbnail->meta_value, true );
    }
    //删除图片附件
    $attachments = $wpdb->get_results( "SELECT * FROM $wpdb->posts WHERE post_parent = $post_ID AND post_type = 'attachment'" );
    foreach ( $attachments as $attachment ) {
        wp_delete_attachment( $attachment->ID, true );
    }
    $wpdb->query( "DELETE FROM $wpdb->postmeta WHERE meta_key = '_thumbnail_id' AND post_id = $post_ID" );
}
add_action('before_delete_post', 'delete_post_and_attachments');