Sets a user defined callback function that is called when either a client or a server message is received.
bool sybase_set_message_handler(callback $handler, int $msg_type [, resource $conn])
int – message_number
int – severity
int – state
int – line_number
string – description
SYB_CLIENTMSG_CB – a client message callback
SYB_SERVERMSG_CB – a server message callback
TRUE – callback function installed successfully.
FALSE – failed to install callback function.