int mysql_ping(MYSQL * mysql);
Checks whether the connection to the server is working. If it has gone down, and global option reconnect is enabled an automatic reconnection is attempted.
Returns zero on success, nonzero if an error occured.
This function can be used by clients that remain idle for a long while, to check whether the server has closed the connection and reconnect if necessary.
If a reconnect occurred the thread_id will change. Also resources bundled to the connection (prepared statements, locks, temporary tables, ...) will be released.