Error message

PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT ml.*, m.load_functions AS load_functions, m.to_arg_functions AS to_arg_functions, m.access_callback AS access_callback, m.access_arguments AS access_arguments, m.page_callback AS page_callback, m.page_arguments AS page_arguments, m.delivery_callback AS delivery_callback, m.tab_parent AS tab_parent, m.tab_root AS tab_root, m.title AS title, m.title_callback AS title_callback, m.title_arguments AS title_arguments, m.theme_callback AS theme_callback, m.theme_arguments AS theme_arguments, m.type AS type, m.description AS description FROM {menu_links} ml LEFT OUTER JOIN {menu_router} m ON m.path = ml.router_path WHERE (ml.menu_name = :db_condition_placeholder_0) ORDER BY p1 ASC, p2 ASC, p3 ASC, p4 ASC, p5 ASC, p6 ASC, p7 ASC, p8 ASC, p9 ASC; Array ( [:db_condition_placeholder_0] => menu-footer ) in _menu_build_tree() (line 1449 of /var/www/html/includes/menu.inc).