WordPress：删除文章的同时删除文章中图片、缩略图、附件内容

WordPress删除文章时不会同时删除文章中自带的附件、图片、缩略图。所以在删除文章会留下大量的图片附件内容在服务器上占用空间，导致网站运行缓慢，对搜索引擎不友好。所以需要做如下改造达到删除文章的同时删除文章中的图片、缩略图、附件内容。
将以下代码加入到主题的functions.php中。
//同时删除文章中附件
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');