Cannot connect to database !!

exception 'PDOException' with message 'SQLSTATE[HY000] [2002] php_network_getaddresses: getaddrinfo failed: Name or service not known' in /home/worldtamilshistoricalsociety/worldtamilshistoricalsociety.com/wths_account/php/Connection.simple.php:22 Stack trace: #0 /home/worldtamilshistoricalsociety/worldtamilshistoricalsociety.com/wths_account/php/Connection.simple.php(22): PDO->__construct('mysql:host=gtra...', 'gtrafix', 'Gtrafix@invoice...') #1 /home/worldtamilshistoricalsociety/worldtamilshistoricalsociety.com/wths_account/index.php(6): dbConnect() #2 {main}