Problem with database!

PDOException: PDO::__construct(): Error while reading greeting packet. PID=1575911 in /home/usp/web/server.usp.ro/public_html/class/database.php:8
Stack trace:
#0 /home/usp/web/server.usp.ro/public_html/class/database.php(8): PDO->__construct()
#1 /home/usp/web/server.usp.ro/public_html/index.php(7): DataBase->__construct()
#2 {main}

Next PDOException: SQLSTATE[HY000] [2006] MySQL server has gone away in /home/usp/web/server.usp.ro/public_html/class/database.php:8
Stack trace:
#0 /home/usp/web/server.usp.ro/public_html/class/database.php(8): PDO->__construct()
#1 /home/usp/web/server.usp.ro/public_html/index.php(7): DataBase->__construct()
#2 {main}