WordPress at a glance
function is not described

update_blog_public() WP 3.0.0

Update this blog's 'public' setting in the global blogs table.

Public blogs have a setting of 1, private blogs are 0.

No Hooks.

Return

Nothing (null).

Usage

update_blog_public( $old_value, $value );
$old_value(int) (required)
$value(int) (required)
The new public value

Code of update blog public: wp-includes/ms-functions.php VER 5.0.3

<?php
function update_blog_public( $old_value, $value ) {
	update_blog_status( get_current_blog_id(), 'public', (int) $value );
}