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filter is not described

get_main_network_id filter-hook . WP 4.3.0

Filters the main network ID.

Usage

add_filter( 'get_main_network_id', 'filter_function_name_6686' );
function filter_function_name_6686( $main_network_id ){
	// filter...

	return $main_network_id;
}
$main_network_id(int)
The ID of the main network.

Where the hook is called

get_main_network_id()
wp-includes/functions.php 4561
return (int) apply_filters( 'get_main_network_id', $main_network_id );

Where the hook is used (in WP core)

Does not used.