Retrieves the current thread ID. If the connection is lost, and a reconnect with mysql_ping is executed, the thread ID will change. This means only retrieve the thread ID when needed.
The MySQL connection. If the link identifier is not specified, the last link opened by mysql_connect is assumed. If no such link is found, it will try to create one as if mysql_connect had been called with no arguments. If no connection is found or established, an E_WARNING level error is generated.
The thread ID on success or false on failure.