Redirect to single page if one page in search results

//destination file: functions.php
add_action('template_redirect', 'single_result');  
function single_result() {  
	if (is_search()) {  
		global $wp_query;  
		if ($wp_query->post_count == 1) {  
			wp_redirect( get_permalink( $wp_query->posts['0']->ID ) );  
		}  
	}  
}