WordPress at a glance
function is not described

get_current_network_id() WP 4.6.0

Retrieves the current network ID.

No Hooks.

Return

Int. The ID of the current network.

Usage

get_current_network_id();

Code of get current network id: wp-includes/load.php WP 5.2.2

<?php
function get_current_network_id() {
	if ( ! is_multisite() ) {
		return 1;
	}

	$current_network = get_network();

	if ( ! isset( $current_network->id ) ) {
		return get_main_network_id();
	}

	return absint( $current_network->id );
}