error in sql query

SELECT oid
					FROM orders
					WHERE security_id = 'ef669efa25609673cd58e828bac7a334'

mysql error : MySQL server has gone awayError Details

#	Function	Location
1	database->query()	/home/sermon/public_html/cart/model/orders.php:147
2	orders::set_orderid()	/home/sermon/public_html/cart/index.php:528