其中一件事很奇怪。不，它不会删除文件，也不会将其从服务器中删除。它实际上只是删除**元条目

/**
 * Remove metadata matching criteria from a post.
 *
 * You can match based on the key, or key and value. Removing based on key and
 * value, will keep from removing duplicate metadata with the same key. It also
 * allows removing all metadata matching key, if needed.
 *
 * @since 1.5.0
 *
 * @param int    $post_id    Post ID.
 * @param string $meta_key   Metadata name.
 * @param mixed  $meta_value Optional. Metadata value. Must be serializable if
 *                           non-scalar. Default empty.
 * @return bool True on success, false on failure.
 */
function delete_post_meta( $post_id, $meta_key, $meta_value = \'\' ) {
    // Make sure meta is added to the post, not a revision.
    if ( $the_post = wp_is_post_revision($post_id) )
        $post_id = $the_post;

    return delete_metadata(\'post\', $post_id, $meta_key, $meta_value);
}