WordPress函数wp_delete_attachment()代码实现通过id进行删除附件

用法：

<?php wp_delete_attachment( $attachmentid, $force_delete ); ?>

参数：

$attachmentid

(integer) (必填) 要删除的附件ID

默认值:None

$force_delete

(bool) (可选) 是否绕过回收站并强制删除

默认值: false

源文件：

/**
 * Trash or delete an attachment.
 *
 * When an attachment is permanently deleted, the file will also be removed.
 * Deletion removes all post meta fields, taxonomy, comments, etc. associated
 * with the attachment (except the main post).
 *
 * The attachment is moved to the trash instead of permanently deleted unless trash
 * for media is disabled, item is already in the trash, or $force_delete is true.
 *
 * @since 2.0.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param int  $post_id      Attachment ID.
 * @param bool $force_delete Optional. Whether to bypass trash and force deletion.
 *                           Default false.
 * @return mixed False on failure. Post data on success.
 */
function wp_delete_attachment( $post_id, $force_delete = false ) {
	global $wpdb;

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

	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() )
		delete_transient( 'dirsize_cache' );

	/**
	 * Fires before an attachment is deleted, at the start of wp_delete_attachment().
	 *
	 * @since 2.0.0
	 *
	 * @param int $post_id Attachment ID.
	 */
	do_action( 'delete_attachment', $post_id );

	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 );

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

	$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 );
	$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 );

	$uploadpath = wp_upload_dir();

	if ( ! empty($meta['thumb']) ) {
		// Don't delete the thumb if another attachment uses it.
		if (! $wpdb->get_row( $wpdb->prepare( "SELECT meta_id FROM $wpdb->postmeta WHERE meta_key = '_wp_attachment_metadata' AND meta_value LIKE %s AND post_id <> %d", '%' . $wpdb->esc_like( $meta['thumb'] ) . '%', $post_id)) ) {
			$thumbfile = str_replace(basename($file), $meta['thumb'], $file);
			/** This filter is documented in wp-includes/functions.php */
			$thumbfile = apply_filters( 'wp_delete_file', $thumbfile );
			@ unlink( path_join($uploadpath['basedir'], $thumbfile) );
		}
	}

	// Remove intermediate and backup images if there are any.
	if ( isset( $meta['sizes'] ) && is_array( $meta['sizes'] ) ) {
		foreach ( $meta['sizes'] as $size => $sizeinfo ) {
			$intermediate_file = str_replace( basename( $file ), $sizeinfo['file'], $file );
			/** This filter is documented in wp-includes/functions.php */
			$intermediate_file = apply_filters( 'wp_delete_file', $intermediate_file );
			@ unlink( path_join( $uploadpath['basedir'], $intermediate_file ) );
		}
	}

	if ( is_array($backup_sizes) ) {
		foreach ( $backup_sizes as $size ) {
			$del_file = path_join( dirname($meta['file']), $size['file'] );
			/** This filter is documented in wp-includes/functions.php */
			$del_file = apply_filters( 'wp_delete_file', $del_file );
			@ unlink( path_join($uploadpath['basedir'], $del_file) );
		}
	}

	wp_delete_file( $file );

	clean_post_cache( $post );

	return $post;
}