Problem with oracle plugin


I’m new user of nagios. I have already configured everything and it’s working good. But I have a problem with check_oracle_generic plugin. I have installed oracle client, php to have possibility to use oci() funcions( but I’m not shure if php is right installed). I have an error: Return code of 255 is out of bounds. What does it mean? I don’t have any idea… My sql query are good, I have connection to oracle serwer( right password and username). What can I do? Maybe I should install something else?