wp_delete_attachment

wp_delete_attachment：此函式從WordPress資料庫中刪除附件。它將附件ID作為引數，並從資料庫中刪除附件的後設資料、釋出資料和檔案資料。

銷燬或刪除一個附件。

當一個附件被永久刪除時，該檔案也將被刪除。刪除會刪除所有與附件相關的文章元欄位、分類法、評論等（除了主帖）。

除非媒體的回收站被禁用，專案已經在回收站中，或者$force_delete為真，否則附件會被移到回收站而不是永久刪除。”

function wp_delete_attachment( $post_id, $force_delete = false ) {
	global $wpdb;

	$post = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM $wpdb->posts WHERE ID = %d", $post_id ) );

	if ( ! $post ) {
		return $post;
	}

	$post = get_post( $post );

	if ( 'attachment' !== $post->post_type ) {
		return false;
	}

	if ( ! $force_delete && EMPTY_TRASH_DAYS && MEDIA_TRASH && 'trash' !== $post->post_status ) {
		return wp_trash_post( $post_id );
	}

	/**
	 * Filters whether an attachment deletion should take place.
	 *
	 * @since 5.5.0
	 *
	 * @param WP_Post|false|null $delete       Whether to go forward with deletion.
	 * @param WP_Post            $post         Post object.
	 * @param bool               $force_delete Whether to bypass the Trash.
	 */
	$check = apply_filters( 'pre_delete_attachment', null, $post, $force_delete );
	if ( null !== $check ) {
		return $check;
	}

	delete_post_meta( $post_id, '_wp_trash_meta_status' );
	delete_post_meta( $post_id, '_wp_trash_meta_time' );

	$meta         = wp_get_attachment_metadata( $post_id );
	$backup_sizes = get_post_meta( $post->ID, '_wp_attachment_backup_sizes', true );
	$file         = get_attached_file( $post_id );

	if ( is_multisite() && is_string( $file ) && ! empty( $file ) ) {
		clean_dirsize_cache( $file );
	}

	/**
	 * Fires before an attachment is deleted, at the start of wp_delete_attachment().
	 *
	 * @since 2.0.0
	 * @since 5.5.0 Added the `$post` parameter.
	 *
	 * @param int     $post_id Attachment ID.
	 * @param WP_Post $post    Post object.
	 */
	do_action( 'delete_attachment', $post_id, $post );

	wp_delete_object_term_relationships( $post_id, array( 'category', 'post_tag' ) );
	wp_delete_object_term_relationships( $post_id, get_object_taxonomies( $post->post_type ) );

	// Delete all for any posts.
	delete_metadata( 'post', null, '_thumbnail_id', $post_id, true );

	wp_defer_comment_counting( true );

	$comment_ids = $wpdb->get_col( $wpdb->prepare( "SELECT comment_ID FROM $wpdb->comments WHERE comment_post_ID = %d ORDER BY comment_ID DESC", $post_id ) );
	foreach ( $comment_ids as $comment_id ) {
		wp_delete_comment( $comment_id, true );
	}

	wp_defer_comment_counting( false );

	$post_meta_ids = $wpdb->get_col( $wpdb->prepare( "SELECT meta_id FROM $wpdb->postmeta WHERE post_id = %d ", $post_id ) );
	foreach ( $post_meta_ids as $mid ) {
		delete_metadata_by_mid( 'post', $mid );
	}

	/** This action is documented in wp-includes/post.php */
	do_action( 'delete_post', $post_id, $post );
	$result = $wpdb->delete( $wpdb->posts, array( 'ID' => $post_id ) );
	if ( ! $result ) {
		return false;
	}
	/** This action is documented in wp-includes/post.php */
	do_action( 'deleted_post', $post_id, $post );

	wp_delete_attachment_files( $post_id, $meta, $backup_sizes, $file );

	clean_post_cache( $post );

	return $post;
}