mysql_ping() checks whether or
not the connection to the server is working. If it has gone
down, an automatic reconnection is attempted. This function
can be used by scripts that remain idle for a long while, to
check whether or not the server has closed the connection and
reconnect if necessary. mysql_ping()
returns TRUE if the
connection to the server is working, otherwise FALSE.
See also: mysql_thread_id(),
mysql_list_processes().