do_shortcode_tag example

$shortcode_attrs = shortcode_parse_atts( $shortcode[3] );
                if ( ! is_array( $shortcode_attrs ) ) {
                    $shortcode_attrs = array();
                }

                // Specify the post ID of the gallery we're viewing if the shortcode doesn't reference another post already.                 if ( ! isset( $shortcode_attrs['id'] ) ) {
                    $shortcode[3] .= ' id="' . (int) $post->ID . '"';
                }

                $gallery = do_shortcode_tag( $shortcode );
                if ( $html ) {
                    $galleries[] = $gallery;
                } else {
                    preg_match_all( '#src=([\'"])(.+?)\1#is', $gallery, $src, PREG_SET_ORDER );
                    if ( ! empty( $src ) ) {
                        foreach ( $src as $s ) {
                            $srcs[] = $s[2];
                        }
                    }

                    $galleries[] = array_merge(