get_dirsize() WordPress Function

function get_dirsize( $directory, $max_execution_time = null ) {

	// Exclude individual site directories from the total when checking the main site of a network,
	// as they are subdirectories and should not be counted.
	if ( is_multisite() && is_main_site() ) {
		$size = recurse_dirsize( $directory, $directory . '/sites', $max_execution_time );
	} else {
		$size = recurse_dirsize( $directory, null, $max_execution_time );
	}

	return $size;
}